Question

Suppose you repeatedly throw 3 fair coins (simultaneously). How many such throws do expect to do until you get a throw where all coins come up heads?

Answer 1

Number of trails required equals 8.

Step-by-step explanation:

The probability that all three coins have heads as their result equals

`P(E)=P(1)* P(2)* P(3)\\\\P(E)=1/2* 1/2* 1/2\\\\ \therefore P(E)=(1)/(8)`

Now using basic theorem of Geometric probability we have

"If probability of success is p in every trial, then expected number of trials until success is 1/p"

Thus the no of trails until success equals
`(1)/((1)/(8))=8`