Posted by Joe on .
How would I solve these two problems. (We have to simplify our answer)
5/7 divided by 8/21
12/7 divided by 9/21

MathFractions 
Reiny,
I will do the first, you do the second
5/7 divided by 8/21
= (5/7)รท(8/21)
= (5/7)(21/8)
= 15/8 , (the 7 cancelled into the 21) 
MathFractions 
Kelly,
I'd like to learn this. How did you get 15/8. Did you multiply 5 by 3 to get that?

MathFractions 
Reiny,
yes, to multiply fractions, you multiply the numerators, and you multiply the denominators.
e.g.
2/3 x 5/7 = 10/21
in your question of
(5/7)(21/8)
I had 105/56
= 15/8 after dividing top and bottom by 7 
MathFractions 
Kelly,
that's cool. Thanks