Question

A die is rolled 8 times. Find the probability.

P(getting at least 7 even numbers)

Answer 1

you roll 8 dice, the probability of you rolling an even number is 1/2
P(at least 7 evens) = P(7 even numbers) + P(8 even numbers)

P(7 even numbers) = (1/2)^7 * (1/2)
P(8 even numbers) = (1/2)^8

P(7 even numbers) + P(8 even numbers) = (1/2)^7 * (1/2) + (1/2)^8
(1/2)^8 + (1/2)^8
2*(1/2)^8
(1/2)^7