Subject

Mathematics

Class

JEE Class 12

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 Multiple Choice QuestionsMultiple Choice Questions

71.

A random variable X has the probability distribution:

X: 1 2 3 4 5 6 7 8
P(X): 0.15 0.23 0.12 0.10 0.20 0.08 0.07 0.05

For the events E = {X is a prime number} and F = {X < 4}, the probability P (E ∪ F) is
  • 0.87

  • 0.77

  • 0.35

  • 0.35

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72.

The mean and the variance of a binomial distribution are 4 and 2 respectively. Then the probability of 2 successes is

  • 37/256

  • 219/ 256

  • 128/256

  • 128/256


D.

128/256

Given that mean = 4
np = 4 and variance = 2
npq = 2 ⇒ 4q = 2
⇒ q = 1/2

∴ p = 1 - q = 1 - 1/2 = 1/2
also n = 8 Probability of 2 successes

straight P left parenthesis straight X space equals 2 right parenthesis space equals space straight C presuperscript 8 subscript 2 straight p squared straight q to the power of 6
space equals space fraction numerator 8 factorial over denominator 2 factorial space straight x space 6 factorial end fraction space straight x space left parenthesis 1 divided by 2 right parenthesis squared space straight x space left parenthesis 1 divided by 2 right parenthesis to the power of 6
space equals space 28 space straight x 1 over 2 to the power of 8 space equals space 28 over 256

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73.

If the straight line y = mx + c (m > 0) touches the parabola y2 = 8(x + 2), then the minimum value taken by c is

  • 12

  • 8

  • 4

  • 4

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74.

The equation of the plane which contains the line of intersection of the planes x + y + z – 6 = 0 and 2x + 3y + z + 5 = 0 and perpendicular to the xy plane is:

  • x – 2y + 11 = 0

  • x + 2y + 11 = 0

  • x + 2y – 11 = 0

  • x + 2y – 11 = 0

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75.

The curve y = (λ + 1)x2 + 2 intersects the curve y = λx + 3 in exactly one point, if λ equals -

  • {–2, 2}

  • {1}

  • {-2}

  • {-2}

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