Which is larger 3/7 or 13/40 ?

2 Answers
Oct 25, 2017

3/7

Explanation:

Rearrange so that they have the same denominator, then you can easily see which one is bigger.

7 isn't a factor of 40, so you will have to find their lowest common multiple.

The easiest way to do this is to multiply 7 by 40.

This gives 280.
Now multiply the top line by whatever you multiplied the bottom line:

(3times40)/280 and (7 times 13)/280

=120/280 and 91/280

Now you can see that 120/280 is bigger.

Oct 25, 2017

3/7

Explanation:

If a, b, c, d are all positive then note that:

a/b < c/d" " if and only if " "ad < bc

So in our example, we find:

3*40 = 120

7*13 = 91

So:

7 * 13 < 3 * 40

and

13/40 < 3/7