Question

A man has 53 socks in his drawer. they are 21 identical blue, 15 identical black and 17 identical red. the lights are fused and he is completely in dark. how many socks must hetake out so that he has a pair of black socks

Answer 1

Total socks = 53 (21 blue + 15 black + 17 red)

Since there are 21 blue and 17 red socks. Therefore sum is 38

Now, if he take out two more socks then it is 100% sure that he will have two black socks. Thus, he must pick 40 socks in order to ascertain that he has two black socks.

Answer 2

To solve this, you need to assume the worst case scenario. This is picking out all of the blue socks, then all of the red socks, before picking out the black socks.

The answer is therefore the number of red socks + the number of blue socks + 2 (for the number of black socks that need to be picked out to form a pair)

21+17+2=40