Question 16
A shop has 200 pairs of red socks, 200 pairs of yellow socks and 200 pairs of black socks. For a sale, it places 600 socks in a bin: 300 right socks and 300 left socks. Find the largest N such that N matching pairs can always be selected. The socks within a pair must have the same colour; different pairs need not have the same colour.
Editorial note: A wearable pair consists of one left and one right sock of the same colour.
Editorial note: A wearable pair consists of one left and one right sock of the same colour.