I have 5 pairs of chopsticks in my drawer, each pair a different colour. How many chopsticks do I have to draw out in order to guarantee that I have grabbed at least one pair of matching colours?
how is the answer 6?
Look at your worst case scenario, which would be:
I pick chopsticks 5 times and each time I get a different colour.
What would happen on my 6th pick ??
of course I could have reached the case of matching colours before the
case of 5 different colours, so the worst we can have is 6 picks.