Question

Dobby the house-elf has dropped all his socks on the floor in the middle of the night! He has 30 red socks, 22 gold socks and 14 black socks. How many socks would he have to pick up before getting a matching pair?

Answer 1

Given:

Number of red socks = 30 socks
Number of gold socks = 22 socks
Number of black socks = 14 socks
Total number of socks = 66 socks

The probability that he will pick up a red sock is:

One red sock = 30/66
Another red sock = 29/65

The probability that he will pick up a pair is:

30/66 * 29/65 = 0.20