Question

Ethan has 12 coins. There are three 10p coins and nine 20p coins 20p coins. Ethan chooses 3 coins at random. Work out the probability that he takes exactly 50p.​

Answer 1

3/220.

Explanation:

To get exactly 50p he must take 2 20p coins and 1 10p coin.

There are 3! /2! = 3 ways of getting this.

Total number of ways of getting any 3 coins form 12 is 12!/9!3!

= 12*11*10 / 3!

= 220.

So the answer is 3/220.