Question

In a box there are many one-euro, two-euro, and five-euro coins. A dispencer draws coins out of the box - one at a time, and stops when three identical coins are taken out. What is the largest possible amount that can be withdrawn?

The answer is 21, please explain why!!!!!!!!!

Answer 1

We want the biggest amount, so here goes:

1. one-euro

2. one-euro

3. two-euro (he can't pick a one-euro here, otherwise he's done!)

4. two-euro

5. five-euro (he can't pick a two-euro here, otherwise he's done!)

6. five-euro

7. five-euro

1+1+2+2+5+5+5 = 21