Ten coins are tossed. What is the probability of getting at least 8 heads?
Let X be the random variable for getting a head.
Here, n=10, r≥8
r=8,9,10
We know that, 
∴P(X=r) = P(r=8) + P(r=9)÷P(r=10)
21
Ten coins are tossed. What is the probability of getting at least 8 heads?
Let X be the random variable for getting a head.
Here, n=10, r≥8
r=8,9,10
We know that,
∴P(X=r) = P(r=8) + P(r=9)÷P(r=10)