# I can't seem to get the correct answer to this fraction, what am I doing wrong?

• Sep 18th 2011, 08:28 AM
popopopop
I can't seem to get the correct answer to this fraction, what am I doing wrong?
This is the sum with which I'm having trouble:

8 ÷ 3 1/5 = ?

This is how I've tried to do it:

8/1 ÷ 16/5

Then I have found the reciprocal of 8/1:

1/8

Therefore,

1/8 X 16/5 = 16/40

BUT
the answer is not 16/40 but 2 1/2.

40/16 would be 2 1/2.

What do I need to do?

Thanks
• Sep 18th 2011, 08:29 AM
Prove It
Re: I can't seem to get the correct answer to this fraction, what am I doing wrong?
Quote:

Originally Posted by popopopop
This is the sum with which I'm having trouble:

8 ÷ 3 1/5 = ?

This is how I've tried to do it:

8/1 ÷ 16/5

Then I have found the reciprocal of 8/1:

1/8

Therefore,

1/8 X 16/5 = 16/40

BUT
the answer is not 16/40 but 2 1/2.

40/16 would be 2 1/2.

What do I need to do?

Thanks

It's the SECOND fraction you need to invert, not the first...
• Sep 18th 2011, 08:30 AM
e^(i*pi)
Re: I can't seem to get the correct answer to this fraction, what am I doing wrong?
Quote:

Originally Posted by popopopop
This is the sum with which I'm having trouble:

8 ÷ 3 1/5 = ?

This is how I've tried to do it:

8/1 ÷ 16/5

Then I have found the reciprocal of 8/1:

1/8

Therefore,

1/8 X 16/5 = 16/40

BUT
the answer is not 16/40 but 2 1/2.

40/16 would be 2 1/2.

What do I need to do?

Thanks

You need to flip the fraction you're dividing by - in this case 16/5
• Sep 18th 2011, 08:32 AM
Plato
Re: I can't seem to get the correct answer to this fraction, what am I doing wrong?
You have it backwards.
$\displaystyle \frac{a}{b}\div\frac{c}{d} = \frac{a}{b} \times \frac{d}{c}$
• Sep 18th 2011, 08:38 AM
popopopop
Re: I can't seem to get the correct answer to this fraction, what am I doing wrong?
Thank you, I thought that might be why.

By the way, hello to all.