What are the ways to make 20p using 1p 2p 5p 10p coins?
20x1p
18x1p + 1x2p
16x1p + 2x2p
15x1p + 1x5p
14x1p + 3x2p
13x1p + 1x2p + 1x5p
12x1p + 4x2p
11x1p + 2x2p + 1x5p
10x1p + 2x5p
10x1p + 1x10p
8x1p + 6x2p
8x1p + 1x2p+ 2x5p
8x1p + 1x2p+ 1x10p
6x1p + 7x2p
6x1p + 2x2p+ 2x5p
6x1p + 2x2p+ 1x10p
5x1p + 3x5p
5x1p + 1x5p + 1x10p
4x1p + 8x2p
4x1p + 3x2p + 2x5p
4x1p + 3x2p + 1x10p
3x1p + 1x2p + 3x5p
3x1p + 1x2p + 1x5p + 1x10p
2x1p + 9x2p
2x1p + 4x2p + 2x5p
2x1p + 4x2p + 1x10p
1x1p + 2x2p + 3x5p
1x1p + 2x2p + 1x5p + 1x10p
10x2p
5x2p + 2x5p
5x2p + 1x10p
4x5p
2x5p + 1x10p
2x10p
I think those are all the ways but there may be more.
* * * * *
There are at least 5 more:
9*1p + 3*2p + 1*5p
7*1p + 4*2p + 1*5p
3*1p + 6*2p + 1*5p
1*1p + 7*2p + 1*5p
1*20p