JEE Main Session 2 31st January 2023 Shift 2 Question Paper and Answer Key

JEE MAIN 31st January 2023 Shift 2

Physics

SECTION-A

IMPORTANT INSTRUCTIONS:

(1) The test is of 3 hours duration:

(2) The Test Booklet consists of 90 questions. The maximum marks are 300.

(3) There are three parts in the question paper consisting of Physics, Chemistry and Mathematics having 30 questions in each part of equal weightage. Each part (subject) has two sections.

(i) Section-A: This section contains 20 multiple choice questions which have only one correct answer. each question carries 4 marks for correct answer and 1 mark for wrong answer.

(ii) Section-B: This section contains 10 questions. In Section-B, attempt any five questions out of 10. The answer to each of the questions is a numerical value. Each question carries 4 marks for correct answer and 1 mark for wrong answer. For Section-B, the answer should be rounded off to the nearest integer.

1. Given below are two statements:

Statement I: In a typical transistor, all three regions emitter, base and collector have same doping level. 

Statement II: In a transistor, collector is the thickest and base is the thinnest segment.  In the light of the above statements, choose the most appropriate answer from the options given below.

(1) Both Statement I and Statement II are correct 

(2) Statement I is incorrect but Statement II is correct 

(3) Statement I is correct but Statement II is incorrect 

(4) Both Statement I and Statement II are incorrect

Answer: (2)

2. If the two metals A and B are exposed to radiation of wavelength 350 nm. The work functions of metals A and B are 4.8eV and 2.2eV. Then choose the correct option.

(1) Both metals A and B will emit photo-electrons 

(2) Metal A will not emit photo-electrons 

(3) Metal B will not emit photo-electrons 

(4) Both metals A and B will not emit photo-electrons

Answer: (2)

3. Heat energy of 735 J is given to a diatomic gas allowing the gas to expand at constant pressure. Each gas molecule rotates around an internal axis but do not oscillate. The increase in the internal energy of the gas will be :

(1)   525 J

(2)   441 J

(3)   572 J

(4)   735 J

Answer: (1)

4. Match List I with List II

Choose the correct answer from the options given below:

(1) A – III, B – I, C – IV, D – II

(2) A – II, B – III, C – IV, D – I 

(3) A – IV, B – II, C – I, D – III

(4) A – I, B – IV, C – III, D – II

Answer: (1)

5. A stone of mass 1 kg is tied to end of a massless string of length 1 m. If the breaking tension of the string is 400 N, then maximum linear velocity, the stone can have without breaking the string, while rotating in horizontal plane, is :

(1)   40 ms1

(2)   400 ms1

(3)   20 ms1

(4)   10 ms1

Answer: (3)

6. A microscope is focused on an object at the bottom of a bucket. If liquid with refractive index 5/3 is poured inside the bucket, then microscope have to be raised by 30 cm to focus the object again. The height of the liquid in the bucket is :

(1)   12 cm

(2)   50 cm

(3)   18 cm

(4)   75 cm

Answer: (4)

7. The number of turns of the coil of a moving coil galvanometer is increased in order to increase current sensitivity by 50%. The percentage change in voltage sensitivity of the galvanometer will be :

(1)   0%

(2)   75%

(3)   50%

(4)   100%

Answer: (1)

8. A body is moving with constant speed, in a circle of radius 10 m. The body completes one revolution in 4s. At the end of 3rd second, the displacement of body (in m) from its starting point is:

(1)   15π

(2)   10√2

(3)   30

(4)   5π

Answer: (2)

9. The H amount of thermal energy is developed by a resistor in 10 s when a current of 4 A is passed through it. If the current is increased to 16 A, the thermal energy developed by the resistor in 10 s will be :

(1)   H/4

(2)   16H

(3)   4H

(4)   H

Answer: (2)

10. A long conducting wire having a current I flowing through it, is bent into a circular coil of N turns. Then it is bent into a circular coil of n turns. The magnetic field is calculated at the centre of coils in both the cases. The ratio of the magnetic field in first case to that of second case is:

(1)   n: N

(2)   n2 : N2

(3)   N2 : n2

(4)   N : n

Answer: (3)

11. A body weight W, is projected vertically upwards from earth’s surface to reach a height above the earth which is equal to nine times the radius of earth. The weight of the body at that height will be :

(1)   W/100

(2)   W/91

(3)   W/3

(4)   W/9

Answer: (1)

12. The radius of electron’s second stationary orbit in Bohr’s atom is R. The radius of 3rd orbit will be

(1)   R/3

(2)   3R

(3)   2.25R

(4)   9R

Answer: (3)

13. A hypothetical gas expands adiabatically such that its volume changes from 08 litres to 27 litres. If the ratio of final pressure of the gas to initial pressure of the gas is 16/81. Then ratio of cp/cv will be

(1)   1/2

(2)   4/3

(3)   3/2

(4)   3/1

Answer: (2)

14. For a solid rod, the Young’s modulus of elasticity is 3.2 × 1011Nm−2 and density is 8 × 103 kg m−3. The velocity of longitudinal wave in the rod will be.

(1)   145.75 × 103 ms1

(2)   18.96 × 103 ms1

(3)   3.65 × 103 ms1

(4)   6.32 × 103 ms1

Answer: (4)

15. A body of mass 10 kg is moving with an initial speed of 20 m/s. The body stops after 5 s due to friction between body and the floor. The value of the coefficient of friction is: (Take acceleration due to gravity g = 10 ms−2)

(1)   0.3

(2)   0.5

(3)   0.2

(4)   0.4

Answer: (4)

16. Given below are two statements :

Statement I : For transmitting a signal, size of antenna (l) should be comparable to wavelength of signal (at least l = λ/4 in dimension)

Statement II : In amplitude modulation, amplitude of carrier wave remains constant (unchanged). 

In the light of the above statements, choose the most appropriate answer from the options given below.

(1) Statement 𝐈 is correct but Statement II is incorrect 

(2) Both Statement I and Statement II are correct 

(3) Statement I is incorrect but Statement II is correct 

(4) Both Statement I and Statement II are incorrect

Answer: (1)

17. An alternating voltage source V=260sin⁡(628t) is connected across a pure inductor of 5mH. Inductive reactance in the circuit is :

(1)   0.318Ω

(2)   6.28Ω

(3)   3.14Ω

(4)   0.5Ω

Answer: (3)

18. Under the same load, wire A having length 5.0 m and cross section 2.5 × 10−5 m2 stretches uniformly by the same amount as another wire B of length 6.0 m and a cross section of 3.0 × 10−5 m2 The ratio of the Young’s modulus of wire A to that of wire B will be :

(1)   1 : 1

(2)   1 : 10

(3)   1 : 2

(4)   1 : 4

Answer: (1)

19. Match List I with List II

Choose the correct answer from the options given below:

(1) A−IV,B – III, C – I, D – II

(2) A−IV,B−I,C – II, D – III 

(3) A – III, B – II, C – I, D – IV

(4) A – II, B – IV, C – III, D – I

Answer: (1)

20. Considering a group of positive charges, which of the following statements is correct?

(1) Both the net potential and the net electric field cannot be zero at a point. 

(2) Net potential of the system at a point can be zero but net electric field can’t be zero at that point. 

(3) Net potential of the system cannot be zero at a point but net electric field can be zero at that point. 

(4) Both the net potential and the net field can be zero at a point.

Answer: (3)

SECTION-B

21. A series LCR circuit consists of R = 80Ω, XL = 100Ω, and XC = 40Ω. The input voltage is 2500 cos⁡(100πt)V. The amplitude of current, in the circuit, is _____A.

Answer: (25)

22. Two bodies are projected from ground with same speeds 40 ms−1 at two different angles with respect to horizontal. The bodies were found to have same range. If one of the body was projected at an angle of 60°, with horizontal then sum of the maximum heights, attained by the two projectiles, is _____m. (Given g = 10 ms−2)

Answer: (80)

23. For the given circuit, in the steady state, |VB – VD| = ________ V.

Answer: (1)

24. Two parallel plate capacitors C1 and C2 each having capacitance of 10μF are individually charged by a 100 V D.C. source. Capacitor C1 is kept connected to the source and a dielectric slab is inserted between it plates. Capacitor C2 is disconnected from the source and then a dielectric slab is inserted in it. Afterwards the capacitor C1 is also disconnected from the source and the two capacitors are finally connected in parallel combination. The common potential of the combination will be ______V. (Assuming Dielectric constant =10)

Answer: (55)

25. Two light waves of wavelengths 800 and 600 nm are used in Young’s double slit experiment to obtain interference fringes on a screen placed 7 m away from plane of slits. If the two slits are separated by 0.35 mm, then shortest distance from the central bright maximum to the point where the bright fringes of the two wavelength coincide will be ______ mm.

Answer: (48)

26. A ball is dropped from a height of 20 m. If the coefficient of restitution for the collision between ball and floor is 0.5, after hitting the floor, the ball rebounds to a height of _____ m

Answer: (5)

27. If the binding energy of ground state electron in a hydrogen atom is 13.6eV, then, the energy required to remove the electron from the second excited state of Li2+ will be : x × 10−1 The value of x is ____.

Answer: (136)

28. A water heater of power 2000 W is used to heat water. The specific heat capacity of water is 4200 J kg−1 K−1. The efficiency of heater is 70%. Time required to heat 2 kg of water from 10∘C to 60°C is _____s. (Assume that the specific heat capacity of water remains constant over the temperature range of the water).

Answer: (300)

29. Two discs of same mass and different radii are made of different materials such that their thicknesses are 1 cm and 0.5 cm respectively. The densities of materials are in the ratio 3:5. The moment of inertia of these discs respectively about their diameters will be in the ratio of x/6. The value of x is ______.

Answer: (5)

30. The displacement equations of two interfering waves are given by  y2 = 5[sin ωt + √3 cos ωt]cm respectively. The amplitude of the resultant wave is ________ cm.

Answer: (20)

Chemistry

SECTION-A

31. Which one of the following statements is incorrect ?

(1) van Arkel method is used to purify tungsten. 

(2) The malleable iron is prepared from cast iron by oxidising impurities in a reverberatory furnace. 

(3) Cast iron is obtained by melting pig iron with scrap iron and coke using hot air blast. 

(4) Boron and Indium can be purified by zone refining method.

Answer: (1)

32. Given below are two statements : one is labelled as Assertion (A) and the other is labelled as Reason (R).

Assertion (A) : The first ionization enthalpy of 3 d series elements is more than that of group 2 metals 

Reason (R) : In 3d series of elements successive filling of d-orbitals takes place.

In the light of the above statements, choose the correct answer from the options given below :

(1) Both (A) and (R) are true but (R) is not the correct explanation of (A) 

(2) Both (A) and (R) are true and (R) is the correct explanation of (A) 

(3) (A) is true but (R) is false 

(4) (A) is false but (R) is true

Answer: (2)

33. Given below are two statements :

Statement I : H2O2 is used in the synthesis of Cephalosporin 

Statement II : H2O2 is used for the restoration of aerobic conditions to sewage wastes. 

In the light of the above statements, choose the most appropriate answer from the options given below:

(1) Both Statement I and Statement II are incorrect

(2) Statement I is incorrect but Statement II is correct

(3) Statement I is correct but Statement II is incorrect 

(4) Both Statement I and Statement II are correct

Answer: (4)

34. A hydrocarbon ‘X’ with formula C6H8 uses two moles H2 on catalytic hydrogenation of its one mole. On ozonolysis, ‘X’ yields two moles of methane dicarbaldehyde. The hydrocarbon ‘X’ is :

(1) cyclohexa-1, 4-diene

(2) cyclohexa – 1, 3 – diene 

(3) 1-methylcyclopenta-1, 4-diene

(4) hexa-1, 3, 5-triene

Answer: (1)

35. Evaluate the following statements for their correctness.

(A) The elevation in boiling point temperature of water will be same for 0.1MNaCl and 0.1M urea. 

(B) Azeotropic mixtures boil without change in their composition. 

(C) Osmosis always takes place from hypertonic to hypotonic solution. 

(D) The density of 32% H2SO4 solution having molarity 4.09M is approximately 1.26 g mL−1

(E) A negatively charged sol is obtained when KI solution is added to silver nitrate solution. 

Choose the correct answer from the options given below :

(1)   A, B and D only

(2)   B and D only

(3)   B, D and E only

(4)   A and C only

Answer: (2)

36. The Lewis acid character of boron tri halides follows the order :

(1) BI3 > BBr3 > BCl3 > BF3                                     

(2) BBr3 > BI3 > BCl3 > BF3 

(3) BCl3 > BF3 > BBr3 > BI3                                      

(4) BF3 > BCl3 > BBr3 > BI3

Answer: (1)

37. When a hydrocarbon A undergoes complete combustion it requires 11 equivalents of oxygen and produces 4 equivalents of water. What is the molecular formula of A ?

(1)   C5H8

(2)   C11H4

(3)   C9H8

(4)   C11H8

Answer: (3)

38. Arrange the following orbitals in decreasing order of energy.

(A) n = 3, l = 0, m = 0

(B) n = 4, l = 0, m = 0

(C) n = 3, l = 1, m = 0

(D) n = 3, l = 2, m = 1

The correct option for the order is :

(1) D > B > C > A             

(2)D > B > A > C                   

(3)A > C > B > D                  

(4) B > D > C > A

Answer: (1)

39. The element playing significant role in neuromuscular function and interneuronal transmission is :

(1)   Li

(2)   Mg

(3)   Be

(4)   Ca

Answer: (4)

40. Given below are two statements :

Statement I : Upon heating a borax bead dipped in cupric sulphate in a luminous flame, the colour of the bead becomes green 

Statement II : The green colour observed is due to the formation of copper(I) metaborate 

In the light of the above statements, choose the most appropriate answer from the options given below:

(1) Both Statement I and Statement II are true

(2) Statement I is true but Statement II is false

(3) Statement 𝐈 is false but Statement II is true

(4) Both Statement I and Statement II are false

Answer: (4)

41. Which of the following compounds are not used as disinfectants ?

(A) Chloroxylenol          (B) Bithional

(C) Veronal                    (D) Prontosil 

(E) Terpineol 

Choose the correct answer from the options given below :

(1)   C, D

(2)   B, D, E

(3)   A, B

(4)   A, B E

Answer: (1)

42. Incorrect statement for the use of indicators in acid-base titration is :

(1) Methyl orange may be used for a weak acid vs weak base titration. 

(2) Phenolphthalein is a suitable indicator for a weak acid vs strong base titration. 

(3) Methyl orange is a suitable indicator for a strong acid vs weak base titration. 

(4) Phenolphthalein may be used for a strong acid vs strong base titration.

Answer: (1)

43. An organic compound [A](C4H11N), shows optical activity and gives N2 gas on treatment with HNO2. The compound [A] reacts with PhSO2Cl producing a compound which is soluble in KOH.

Answer: (4)

44. The normal rain water is slightly acidic and its pH value is 5.6 because of which one of the following?

(1) CO2 + H2O → H2CO3                                              

(2) 2SO2 + O2 + 2H2O → 2H2SO4 

(3) 4NO2 + O2 + 2H2O → 4HNO3                                

(4) N2O5 + H2O → 2HNO3

Answer: (1)

45. Match List I with List II

Choose the correct answer from the options given below:

(1) A – II, B – I, C – IV, D – III

(2) A – IV, B – II, C – III, D – I 

(3) A – II, B – III, C – I, D – IV

(4) A – III, B – IV, C – I, D – II

Answer: (1)

46. Cyclohexylamine when treated with nitrous acid yields (P).On treating (P) with PCC results in (Q). When (Q) is heated with dil. NaOH we get (R) The final product (R) is :

Answer: (2)

47. In the following halogenated organic compounds the one with maximum number of chlorine atoms in its structure is :

(1) Freon-12

(2) Gammaxene

(3) Chloropicrin

(4) Chloral

Answer: (2)

48. In Dumas method for the estimation of N2, the sample is heated with copper oxide and the gas evolved is passed over :

(1)   Copper oxide

(2)   Ni

(3)   Pd

(4)   Copper gauze

Answer: (2)

49. Which of the following elements have half-filled f-orbitals in their ground state ? (Given : atomic number Sm = 62; Eu = 63; Tb = 65; Gd = 64, Pm = 61 )

(A) Sm   (B) Eu (C) Tb  (D) Gd                        (E) Pm

Choose the correct answer from the options given below:

(1)   A and B only

(2)   A and E only

(3)   C and D only

(4)   B and D only

Answer: (4)

50. Compound A, C5H10O5, given a tetraacetate with AC2O and oxidation of A with Br2−H2O gives an acid, C5H10O6 .Reduction of A with HI gives isopentane. The possible structure of A is :

Answer: (3)

SECTION B

51. The rate constant for a first order reaction is 20 min1. The time required for the initial concentration of the reactant to reduce to its 1/32 level is ______ 102 (Nearest integer)

Given : ln 10 = 2.303, log 2 = 0.3010)

Answer: (17)

52. Enthalpies of formation of CCl4( g), H2O(g), CO2(g) and HCl(g) are −105, −242, −394 and − 92 kJ mol−1 The magnitude of enthalpy of the reaction given below is kJmol−1. (nearest integer)

CCl4(g) + 2H2O(g) → CO2(g) + 4HCl(g)

Answer: (173)

53. A sample of a metal oxide has formula M83O1.00. The metal M can exist in two oxidation states + 2 and +3.In the sample of M0.83O1.00, the percentage of metal ions existing in + 2 oxidation state is %. (nearest integer)

Answer: (59)

54. The resistivity of a 0.8M solution of an electrolyte is 5 × 10−3 Ω cm. Its molar conductivity is ______ × 104Ω−1 cm2 mol−1 (Nearest integer)

Answer: (25)

55. At 298 K, the solubility of silver chloride in water is 1.434 × 10−3 g L−1.The value of −log Ksp for silver chloride is ____ (Given mass of Ag is 107.9 g mol−1 and mass of Cl is 35.5 g mol−1)

Answer: (10)

56. If the CFSE of [Ti(H2O)6]3+ is −96.0 kJ/mol, this complex will absorb maximum at wavelength _____ nm. (nearest integer)

Assume Planck’s constant (h) = 6.4 × 1034 Js, Speed of light (c) = 3.0 × 108 m/s and Avogadro’s Constant (NA) = 6 × 1023/mol

Answer: (480)

57. The number of alkali metal(s), from Li, K, Cs, Rb having ionization enthalpy greater than 400 kJ mol−1 and forming stable super oxide is _____

Answer: (2)

58. The number of molecules which gives haloform test among the following molecules is

Answer: (3)

59. Assume carbon burns according to following equation :

2C(g)  + O2(g) → 2CO(g)

When 12 g carbon is burnt in 48 g of oxygen, the volume of carbon monoxide produced is × 101 L at STP [nearest integer]

[Given : Assume co as ideal gas, Mass of c is 12 g mol1, Mass of O is 16 g mol1 and molar volume of an ideal gas STP is 22.7 L mol1]

Answer: (227)

60. Amongst the following, the number of species having the linear shape is

Answer: (5)

Mathematics

SECTION-A

61. The equation e4x + 8e3x + 13e2x − 8ex + 1 = 0, x ∈ ℝ has :

(1) four solutions two of which are negative

(2) two solutions and only one of them is negative

(3) two solutions and both are negative

(4) no solution

Answer: (3)

62. Among the relations

and T = {(a, b): a, b ∈ ℝ, a2 – b2 ∈ ℤ},

(1)   neither S nor T is transitive

(2)   S is transitive but T is not

(3)   T is symmetric but S is not

(4)   both S and T are symmetric

Answer: (3)

63. Let α > 0. If  then α is equal to :

(1)   4

(2)   2√2

(3)   √2

(4)   2

Answer: (3)

64. The complex number  is equal to :

Answer: (3)

65. Let y = y(x) be the solution of the differential equation (3y – 5x)y dx + 2x(x − y)dy = 0 such that y(1) = 1. Then |(y(2)) – 12y(2)| is equal to :

(1)   16√2

(2)   32√2

(3)   32

(4)   64

Answer: (2)

66. 

(1)   does not exist

(2)   is equal to 27

(3)   is equal to 27/2

(4)   is equal to 9

Answer: (2)

67. The foot of perpendicular from the origin O to a plane P which meets the co-ordinate axes at the points A,B,C is (2, a ,4), a ∈ If the volume of the tetrahedron OABC is 144 unit, then which of the following points is NOT on P ?

(1)   (0, 6, 3)

(2)   (0, 4, 4)

(3)   (2, 2, 4)

(4)   (3, 0, 4)

Answer: (4)

68. Let (a, b) ⊂ (0, 2π) be the largest interval for which sin (sin θ)− cos1(sin θ) > 0, θ ∈ (0, 2π), holds. If αx + βx + sin (x – 6x + 10) + cos1(x – 6x + 10) = 0 and α – β = b − a, then α is equal to :

(1)   π/16

(2)   π/48

(3)   π/12

(4)   π/8

Answer: (3)

69. Let the mean and standard deviation of marks of class A of 100 students be respectively 40 and α ( > 0 ), and the mean and standard deviation of marks of class B of n students be respectively 55 and 30 −α. If the mean and variance of the marks of the combined class of 100 + n students are respectively 50 and 350, then the sum of variances of classes A and B is :

(1)   650

(2)   450

(3)   900

(4)   500

Answer: (4)

70. The absolute minimum value, of the function f(x) = |x2 – x + 1| + [x2 – x + 1], where [t] denotes the greatest integer function, in the interval [−1, 2], is

(1)   1/4

(2)   3/2

(3)   5/4

(4)   3/4

Answer: (4)

71. Let H be the hyperbola, whose foci are (1 ± √2, 0) and eccentricity is √2. Then the length of its latus rectum is

(1)   3/2

(2)   2

(3)   3

(4)   5/2

Answer: (2)

72. Let a1, a2, a3, … be an A.P. If a7 = 3, the product a1a4 is minimum and the sum of its first n terms is zero, then n! – 4an(n+2) is equal to :

(1)   9

(2)   33/4

(3)   381/4

(4)   24

Answer: (4)

73. If a point P(α, β, γ) satisfying

lies on the plane 2x + 4y + 3z = 5, then 6α + 9β + 7γ is equal to :

(1)   −1

(2)   11/5

(3)   5/4

(4)   11

Answer: (4)

74. Let :  and  be there vectors. If  is a vector such that,  then  is equal to

(1)   560

(2)   449

(3)   339

(4)   336

Answer: (3)

75. Let the plane P : 8x + α1y + α2y + α2z + 12 = 0 be parallel to the line  If the intercept of P on the y-axis is 1, then the distance between P and L is :

(1)  

(2)  

(3)   6/√14

(4)   √14

Answer: (4)

76. Let P be the plane, passing through the point (1, −1, −5) and perpendicular to the line joining the points (4, 1, −3) and (2, 4, 3). Then the distance of P from the point (3, −2, 2) is

(1)   5

(2)   4

(3)   7

(4)   6

Answer: (1)

77. The number of values of r ∈ {p, q, ~p, ~q} for which ((p ⋀ q) ⇒ (r ⋁ q)) ⋀ ((p ⋀ r) ⇒ q) is a tautology, is:

(1)   3

(2)   4

(3)   1

(4)   2

Answer: (4)

78. The set of all values of a2 for which the line x + y = 0 bisects two distinct chords drawn from a point  on the circle 2x2 + 2y2 – (1 + a)x – (1 – a)y = 0, is equal to:

(1)   (0, 4]

(2)   (4, ∞)

(3)   (2, 12]

(4)   (8, ∞)

Answer: (4)

79. If  x > 0, then ∅ʹ(π/4) is equal to:

Answer: (1)

80. Let f : ℝ − {2, 6} → ℝ be real valued function defined as  Then range of f is

Answer: (4)

SECTION-B

81. Let A = [aij], aij ∈ Z ∩ [0, 4], 1 ≤ i, j ≤ The number of matrices A such that the sum of all entries is a prime number p ∈ (2, 13) is

Answer: (204)

82. Let A be a n × n matrix such that |A| = 2. If the determinant of the matrix Adj(2 ∙ Adj(2 A1)) ∙ is 284, then n is equal to

Answer: (84)

83. If the constant term in the binomial expansion of  is −84 and the coefficient of x3l is 2αβ, where β < 0 is an odd number, then |αl – β| is equal to

Answer: (98)

84. Let S be the set of all a ∈ N such that the area of the triangle formed by the tangent at the point P(b, c), b, c ∈ ℕ, on the parabola y = 2ax and the lines x = b, y = 0 is 16 unit2, then  is equal to

Answer: (146)

85. Let the area of the region {(x, y) : |2x – 1| ≤ y ≤ |x2 – x|, 0 ≤ x ≤ 1} be A. Then (6A + 11)2 is equal to

Answer: (125)

86. The coefficient of x6, in the expansion of  is

Answer: (5040)

87. Let A be the event that the absolute difference between two randomly choosen real numbers in the sample space [0, 60] is less than or equal to a . If  then a is equal to

Answer: (10)

88. If 2n+1Pn1 : 2n1Pn = 11 : 21, then n2 + n + 15 is equal to :

Answer: (45)

89. Let  be three vectors such that  and  If the angle between  is equal to

Answer: (3)

90. The sum 12 – 2 ∙ 32 + 3 ∙ 52 – 4 ∙ 72 + 5 ∙ 92 − … + 15 ∙ 292 is

Answer: (6952)

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