math
posted by deb on .
Compare fractionswrite in order least to greatest. My daughter wrote them incorrectly at first, then we found what the answer should be, but can you explain to her why the answers are what they are. Thank you.
1. 2/5, 1/10, 3/20
answer1/10, 3/20, 2/5
2. 1/3, 3/8, 2/9
answer2/9, 1/3, 3/8

If you plug them into a calculator, you would get decimals. You can use those decimals to see which is least or greater. Atleast that is how I do it.

Convert all the fractions so that they all have the same denominator (the number below the line). That way, you can tell how big they are relative to one another just by looking at the numerator (the number above the line).
(#1.)
2/5, 1/10, and 3/20 can all be converted so that they have a common denominator of 20:
2/5, when you multiply both the top and bottom by 4, becomes 8/20.
1/10, when you multiply both the top and bottom by 2, becomes 2/20.
3/20 already has a denominator of 20.
2/20 < 3/20 < 8/20
so 1/10 < 3/20 < 2/5

(#2.)
Do the same thing as in #1, except now make the common denominator 72, since 9, 3, and 8 can all go into 72 evenly.