Question

10. Jenna flips two pennies 105 times. How

many times can she expect both coins to
come up heads?
​

Answer 1

26

Explanation:

When you flip two coins, you can have 4 different outcomes:

HH

HT

TH

TT

All outcomes are equally likely, but notice that if you do not keep track of which coin is which, you will get 1/4 of the flips to be both heads, 1/4 of the flips to be both tails, and 1/2 of the flips to be one heads and one tails.

p(both heads) = 1/4

With 105 flips, the expected number of both heads is

105 * 1/4 = 26.25

Answer: 26