# Puzzle ZNRA

?

In the land of BrainBashers, stamps are available in denominations of 3p, 9p, 11p, 17p, and 21p (just the five different values).

For three denominations of stamp I was asked to buy eight of each, and for the other two denominations I was asked to buy nine of each.

Unfortunately, I forgot which I was supposed to buy eight of, and which to buy nine of!!

Luckily I had been given the exact money required to buy the stamps, £5.00, so the shopkeeper was able to work out the stamps I needed.

Which stamps did I have to buy?

Eight lots of 11p, 17p and 21p and nine lots of 3p and 9p.

Reasoning
For three denominations of stamp I was asked to buy 8 of each, and for the other two denominations I had to buy 9 of each.

So I had to buy at least 8 of all five denominations.

This would be for a total of 8 x (3 + 9 + 11 + 17 + 21) = 488p = £4.88.

The remaining 12p has to buy the remaining 2 stamps, which must have been 3p and 9p.

Double-Checking
9 x 3 = 27
9 x 9 = 81
8 x 11 = 88
8 x 17 = 136
8 x 21 = 168

For a total of 27 + 81 + 88 + 136 + 168 = 500p = £5.

Note: BrainBashers has a Dark Mode setting.