# Math Help - [SOLVED] coin probability problem

1. ## [SOLVED] coin probability problem

Kaplan Page 136 #19

If 3 coins are tossed simultaneously, what is the probability of getting exactly 2 tails?

The answer is 3/8. Instead of listing all the cases, is there a faster way to solve this problem?

Thanks in advance

2. Every coin flip has a $\frac{1}{2}$ chance of turning up heads or tails.

You can have T, T, H or T, H, T or H, T, T
Each of these 3 outcomes has a probability of $\frac{1}{2} \times \frac{1}{2} \times \frac{1}{2}$

So probability for exactly 2 tails for 3 coin tosses = $3 \left( \frac{1}{2} \right)^3 = \frac{3}{8}$