Probability (Class 12)

JEE Main 2025 (Online) 22nd January Morning ShiftMCQMedium📈 Topic in 13% papers+4−1

Ques. 1JEE Main 2025, 22 January (Morning Shift)

A coin is tossed three times. Let X denote the number of times a tail follows a head. If and 2 denote the mean and variance of X, then the value of 64 ( + 2 ) is:

Answer

(4) 48

Solution

Count "HT" in the 8 outcomes: X=1 for HHT, HTH, HTT, THT; otherwise X=0.

P(X=1)=P(X=0)= 12, a Bernoulli variable with p= 12

= 12, 2=p(1-p)= 14

64( + 2)=64 34=48

Answer: (4)

Keep practising — Probability (Class 12)

Ques. 2JEE Main 2025, 22 January (Morning Shift)

Two balls are selected at random one by one without replacement from a bag containing 4 white and 6 black balls. If the probability that the first selected ball is black, given that the second selected ball is also black, is mn, where (m,n)=1, then m+n is equal to :

Ques. 3JEE Main 2025, 22 January (Evening Shift)

If A and B are two events such that P(A B)=0.1, and P(A B) and P(B A) are the roots of the equation 12x2-7x+1=0, then the value of P( A B)P( A B) is :

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