Posted by Danielle on .
Seven standard, sixsided dice are rolled, one after the other. What is the probability that:
a) exactly one of them shows a six?
c) there is at least one that shows a six?

Math 
Reiny,
prob(6) = 1/6
prob(not6) = 5/6
a) exactly 1 out of 7 tries to be 6
= C(7,1) * (1/6)^1 * (5/6)^6
= .3907 rounded to 4 decimals
b) at least one 6 > 1  prob(all not6)
= 1  C(7,7) * (1/6)^0 * (5/6)^7
= 1  .2791
= .7209