Question

Ten coins are tossed simultaneously. Find the probability of getting at least seven heads.

Answer 1

7/10 is the probability

Answer 2

Best Answer: P(getting a head) = p = 1/2

q = 1-p = 1-1/2 = 1/2

n = 10

The general form of binomial distribution for determining the probability of r successes is

P(r) = nCr*q^(n-r)*p^r

Required probability = P(r >/= 7) = P(r=7)+P(r=8)+P(r=9)+P(r=10)

Since p=q=1/2,

q^(n-r)*p^r = (1/2)^10

P(r >/= 7) = (1/2)^10*(10C7+10C8+10C9+10C10)

= 1/1024*(120+45+10+1)

= 1/1024*(176)

= 176 / 1024

= 0.171875