Question 1024290: I need 45 cents worth of stamps to send a letter to my pen pal. I looked at the stamps my mother has, and they are all 15-cent, 10-cent, and 5-cent stamps. How many different combinations of stamps can I put on my letter?
Answer by Edwin McCravy(20055)   (Show Source):
You can put this solution on YOUR website!
If you don't use any 15c stamps, you can put from
0 through 4 10c stamps and the rest in 5c stamps.
That's 5 ways.
If you use exactly 1 15c stamp, you have 20c left,
which you can get by putting put from 0 through 3
10c stamps and the rest, if any, in 5c stamps.
That's 4 ways.
If you use exactly 2 15c stamp, you have 15c left,
which you can get by putting put from 0 - 1 10c
stamps and the rest in 5c stamps.
That's 2 ways
Or you can use 3 15c stamps.
That's 1 more way.
Total: 5 + 4 + 2 + 1 = 12 ways.
Edwin
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