Yesterday I was asked to buy some stamps.
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?
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I bought at least 8 of each stamp.
Eight lots of 11p, 17p and 21p and nine lots of 3p and 9p.
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.
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.
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