help please
5 over 21 divided by 15 over 7

Question

help please
5 over 21 divided by 15 over 7

aaronandyson · Answer

$$\frac{ 5 }{ 21 } \div \frac{ 15 }{ 7 }$$

k_lynn · Answer

$$\frac{ 5 }{ 21 }\div \frac{ 15 }{ 7 }$$
That?

anonymous · Answer

yea just like that

aaronandyson · Answer

Reciprocate it
I mean do this
$$\frac{ 5 }{ 21 } \div \frac{ 7 }{ 15 }$$

aaronandyson · Answer

I think that div signs changes to multiply 
@k_lynn 
I am right or wrong?

anonymous · Answer

I thought when dividing fractions you cross multiply but I'm not so good with math lol so i might be wrong

k_lynn · Answer

To divide fractions, you can actually multiply by the reciprocal.  So like this.  $$\frac{ 5 }{ 21 }\times \frac{ 7 }{ 15 }$$Now all you need to do is multiply the numerators and then multiply the denominators.  And yes, you're right @AaronAndyson :)

aaronandyson · Answer

So now
 What is 7 times 3?
and 5 times 15?

k_lynn · Answer

You don't cross multiply, because you know all the numbers.  If you had something that looked like this... $$\frac{ x }{ 34 }=\frac{ 2 }{ 7 }$$Then you would cross multiply.

k_lynn · Answer

So now to finish the question, all you need to do is this.  $$\frac{ 5\times7 }{ 21\times15 }$$

anonymous · Answer

35/ 315 is the answer i got is that correct

aaronandyson · Answer

O.O
Try again.

aaronandyson · Answer

7 times 3 is 21
5 times 3 is 15

anonymous · Answer

im confused lol

aaronandyson · Answer

$$5 \times 7 \over 21 \times 15$$

aaronandyson · Answer

is

aaronandyson · Answer

$$1 \times 1 \over 3 \times 3$$

aaronandyson · Answer

as 7 times 3 is 21
5 times 3 is 15

aaronandyson · Answer

so we just just do this
$$3 \times 3$$

aaronandyson · Answer

what is 3 times 3?

anonymous · Answer

i did that and i got 35 for 5 * 7 and 315 for 21 *15 i don't get were i went wrong I'm confused sorry I'm really bad at math :/

aaronandyson · Answer

Okay
35/315 is ?

aaronandyson · Answer

35 times what is 315?

aaronandyson · Answer

You're method is correct but mine is a bit simple.

aaronandyson · Answer

35 times 9 is 315
Hence the answer is 9

anonymous · Answer

35 * 9 = 315

aaronandyson · Answer

Correct!
So what is the answer?

anonymous · Answer

@AaronAndyson

anonymous · Answer

ohhh okay thank you

aaronandyson · Answer

We have
35/315
we know that 35 times 9 is 315
so can you tell me the answer now?

anonymous · Answer

so it would be 35 over 9 or just 9

aaronandyson · Answer

Just 9 as 
We divide both by 35.

anonymous · Answer

i got 1 over 9

anonymous · Answer

it was correct lol thank you

aaronandyson · Answer

No problem lol.