Question

The probability of getting almost 4heads when tossing 7coins is
a)57/64. b)99/128. c)5/16.
d)1/2​

Answer 1

Answer:The answer will be option b 99/128

Step-by-step explanation:

Answer 2

Answer:

If I've got your question correctly, then you're looking for atmost 4heads when tossing 7 coins.

Hence, here n=7

Now, to have atmost 4 heads, we need to remember that getting no head and getting 4 heads are possibilities. Hence, here we need to calculate P(X=0,1,2,3,4) which will be 1-P(X=5,6,7).

Now, probability of getting a head in a coin toss is 1/2 which is a success here.

So p= 1/2 and q= 1/2 as well.

So using binomial expression, P(X=r)= nCr (p)^r (q)^(n-r), we can find as follows, P(X=5)= 21/128, P(X=6)= 7/128, P(X=7)= 1/128, the cumulative of which gives us 29/128.

Hence, P(X=0,1,2,3,4) = 1-(29/128) = 99/128