by RonPurewal Mon Sep 29, 2008 5:58 am
the above method is great.
you can also realize that this problem is a thinly veiled way of asking you for the least common multiple of the two prices. in fact, that shouldn't be that hard to see here: you're looking to spend equal amounts of money on the two types of items, so, those equal amounts must be multiples of both prices.
since you're looking for the smallest such multiple, you're looking for the smallest number that's a multiple of both prices - which is the exact definition of the least common multiple.
to find the least common multiple, you could just experiment with numbers, but, if you're looking for a more systematic way, you could use prime factorizations:
600 = 6 x 100 = (2 x 3)(2^2 x 5^2) = 2^3 x 3 x 5^2
375 = 3 x 125 = 3 x 5^3
the least common multiple takes the highest power of every prime number appearing anywhere in these factorizations. therefore, the least common multiple is 2^3 x 3 x 5^3, or 3000.