Four coins are tossed simultaneously. What is the probability of getting exactly 2 heads?

Options

A. `(1)/(2)`
B. `(1)/(4)`
C. `(1)/(8)`
D. `(3)/(8)`

Answer

D

Explanation

From Binomial Distribution, we have
`P(X=r)=.^(n)C_(r)(p)^(r)(q)^(n-r),r le n `
In the given question
`n=4, r=2 p="prob of head"=(1)/(2), q="prob. of tail"=(1)/(2)`
`P(X=2)=.^(4)C_(2)xx((1)/(2))^(2)=(6)/(16)=(3)/(8)`