Subject

Mathematics

Class

JEE Class 12

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 Multiple Choice QuestionsMultiple Choice Questions

61.

There is an error of ± 0.04cm in the measurement of the diameter of a sphere. When radius is 10cm, the percentage error in the volume of the sphere is

  • ± 1.2

  • ± 1.0

  • ± 0.8

  • ± 0.6


62.

The function fx = x3 +ax2 + bx +c, a2  3b has

  • one maximum value

  • one minimum value

  • no extreme value

  • one maximum and one minimum value


63.

The maximum value of log(x)x, 0 < x <  is

  • e

  • 1

  • e - 1


64.

z = tany +ax +y - ax  zxx - a2zyy =?

  • 0

  • 2

  • zx + zy = 0

  • zxzy


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65.

In a quadrilateral ABCD, the point P divides DC in the ratio 1 : 2 and Q is the mid point of AC. IfAB + 2AD + BC - 2DC = kPQ, then k is equal

  • - 6

  • - 4

  • 6

  • 4


66.

The angle between the lines whose direction cosines satisfy the equations l + m + n = 0, l2 + m2 - n2 = 0 is

  • π6

  • π4

  • π3

  • π2


67.

If a = - i^ + j^ + 2k^, b = 2i^ - j^ - k^, and c = - 2i^ + j^ + 3k^, then the angle between 2a - c and a + b is

  • π4

  • π3

  • π2

  • 3π2


68.

If m1, m2, m3 and m4 are respectively the magnitudes of the vectorsa1 = 2i^ - j^ + k^, a2 = 3i^ - 4j^ - 4k^,a3 = i^ + j^ - k^ and  a4 = - i^ +  3j^ + k^, then the correct order of m1, m2, m3 and m4 is 

  • m3 < m1 < m4 < m2

  • m3 < m1 < m2 < m4

  • m3 < m4 < m1 < m2

  • m3 < m4 < m2 < m1


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69.

Suppose a = λi^ - 7j^ + 3k^, b = λi^ + j^ + 2λk^. Ifthe angle between a and b is greater than 90°, then A satisfies the inequality

  • - 7 < λ < 1

  • λ > 1

  • 1 < λ < 7

  • - 5 < λ < 1


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70.

The volume of the tetrahedron having the edgei^ + 2j^ - k^,  i^ + j^ + k^,  i^ - j^ + λk^ as coterminous, is 23cubic unit. Then λ = ?

  • 1

  • 2

  • 3

  • 4


A.

1

Let, a = i^ + 2j^ - k^,  b = i^ + j^ + k^ and c =   i^ - j^ + λk^Since, volume of tetrahedron = 16a b c23 = 1612- 11111- 1λ 23 = 161λ + 1 - 2λ - 1 - 1- 1 - 1 4 = - λ + 5  λ = 1


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