If eight coins are tossed together, then the probability of getting exactly 3 heads is
If eight coins are tossed together, then the probability of getting exactly 3 heads is
A. `1/256`
B. `7/32`
C. `5/32`
D. `3/32`
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We know that, probability distribution P(X=r)=`""^(n)C_(r)(p)^( r)q^(n-r)`
Here, n=8,r=3,p=`1/2` and q=`1/2`
`therefore` Required probability=`""^(8)C_(3)(1/2)^(8-3)=(8!)/(5!3!)(1/2)^(8)`
`=(8cdot7cdot6)/(3cdot2)cdot1/(16cdot16)=7/32`
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