HKIMO 2017 Grade 6 National Final (Heat) Set 04 Question 5

There are 6 white, 8 yellow and 11 brown chopsticks mixed together. In the dark, what is the least number to take to guarantee four pairs: three pairs of one colour and one pair of a different colour?

Source glossary (English–Vietnamese): Together: cùng nhau; At least: ít nhất.