ShmoopTube

00:03

Here's your shmoop du jour.

00:06

2/5 divided by... 1/15 minus 3/10 equals...what?

00:12

And here are the potential answers...

00:16

Well, this question isn't big on words -- it's just asking whether we can subtract and divide fractions.

00:21

Piece of cake. Because we don't want to make PEMDAS mad,

00:24

we start with the junk inside the parentheses.

00:28

First we have to get a common denominator for 15 and 10.

00:34

Both fit into 30 pretty easily... in that case, let's multiply top and bottom of 1

00:38

over 15 by 2 to become 2 over 30...

00:43

...then we multiply top and bottom of 3 over 10 by 3 to get 9 over 30.

00:49

2 minus 9 is -7... so we can rewrite the problem now as 2 fifths divided by -7 over 30.

00:56

And remember that dividing by a fraction is the same thing as multiplying by its inverse.

01:01

So rewrite the problem as:

01:03

Two fifths TIMES -30 over 7

01:07

And we have -60 over 35

01:10

We can reduce that bad boy to -12 over 7 and voila -- it's answer A.

01:15

Thank goodness. Now we won't have to deal with the wrath of PEMDAS.

Full Transcript