# Reducing Fractions Questions

• October 31st 2008, 09:20 AM
Jman115
Reducing Fractions Questions
Now when I reduce fractions while multiplying I am getting confused. I know I can cross cancel AND do vertical reduction.

Now when i do the problem:

18/12 ÷ 35/70
I reduce to
3/2 ÷ 1/2

I then FLIP...cross cancel and multiply like so:

3/2 • 2/1
Cross cancel the 2's
3/1 • 1/1 = 3/1

This problem is correct. However. When I do the same thing with the following problem, I get an incorrect answer. What am I doing wrong?

240/10 ÷ 65/100
I reduced to
24/1 ÷ 13/20

I then...cross canceled 20 and 24.....flipped...and multiply like so:

6/1 • 13/5
Flip and multiply
6/1 5/13 = 30/13

that is the wrong answer. it should be 36 and 12 over 13.

What did I do wrong and why is it wrong?
• October 31st 2008, 09:42 AM
masters
Quote:

Originally Posted by Jman115
However. When I do the same thing with the following problem, I get an incorrect answer. What am I doing wrong?

240/10 ÷ 65/100
I reduced to
24/1 ÷ 13/20

I then...cross canceled 20 and 24.....flipped...and multiply like so:

6/1 • 13/5
Flip and multiply
6/1 5/13 = 30/13

that is the wrong answer. it should be 36 and 12 over 13.

What did I do wrong and why is it wrong?

$\frac{24}{1} \div \frac{13}{20}=\frac{24}{1} \times \frac{20}{13}$

You cannot "cross/cancel" over division....only multiplication.
• October 31st 2008, 10:15 AM
Jman115
Oh duh, thanks a bunch.
• October 31st 2008, 10:19 AM
HallsofIvy
Quote:

Originally Posted by Jman115
Now when I reduce fractions while multiplying I am getting confused. I know I can cross cancel AND do vertical reduction.

Now when i do the problem:

18/12 ÷ 35/70
I reduce to
3/2 ÷ 1/2

I then FLIP...cross cancel and multiply like so:

3/2 • 2/1
Cross cancel the 2's
3/1 • 1/1 = 3/1

This problem is correct. However. When I do the same thing with the following problem, I get an incorrect answer. What am I doing wrong?

240/10 ÷ 65/100
I reduced to
24/1 ÷ 13/20

I then...cross canceled 20 and 24.....flipped...and multiply like so:

6/1 • 13/5

You haven't "flipped" yet! You can't cancel numbers in the two different fractions until after you have flipped them
24/1 ÷ 13/20= 24/1 x 20/13 and now the 24= 4(6) and 20= 4(5) are both in the numerator- they cannot be canceled.

Quote:

Flip and multiply
6/1 5/13 = 30/13

that is the wrong answer. it should be 36 and 12 over 13.

What did I do wrong and why is it wrong?