math
posted by jennah on .
How to find the value of y in a fraction

I'm going to try to infer a lot here, because the question is so obscure. I assume you're being asked to work out what the denominator of a fraction is when you're presented with the equivalent decimal. So suppose you're given a decimal number like 0.42, and you're asked to express it as a simple fraction x/y in the simplest possible terms. If that's right, the first thing to do is express it as ANY fraction  and the most obvious one in this example would be 42/100. Now try to reduce it to its simplest form  and you do that by finding factors that are common to both the numerator and the denominator. The numerator factorizes as (7 x 6) = (7 x 3 x 2), whereas the denominator is (2 x 2 x 5 x 5). Of these, only a single 2 is common to both the numerator and the denominator, so the best you can do is reduce the fraction to (21/50). Does that help, or are you trying to do something else entirely?