# Thread: Multiply the algebraic fractions

1. ## Multiply the algebraic fractions

I am having a problem multiplying these fractions:

$\displaystyle \frac{x^2y^2}{m^3n} * \frac{5a+5b}{2d^2+2d} =$

This is the process I know for solving these:

1. Factor the numerators and denominators of both fractions.
2. Cross out the common factors. Now I can see what the answer is.

But that isn't working here. I can't find any common factors, so I can't get rid of them:

$\displaystyle \frac{x*x*y*y}{m*m*m*n}* \frac{5(a+b)}{2d(d+1)} =$

The answer is $\displaystyle \frac{y^2}{m^2nx}$ but knowing the answer is useless to me because I don't know how to get there.

What am I doing wrong? Is there a different way to multiply fractions? Am I factoring wrong? Why does an x end up in the denominator?

2. Originally Posted by bryang
The answer is $\displaystyle \frac{y^2}{m^2nx}$ but knowing the answer is useless to me because I don't know how to get there.

What am I doing wrong? Is there a different way to multiply fractions? Am I factoring wrong? Why does an x end up in the denominator?
That answer doesn't make sense to me either. Could it be that there is some other relationship between the variables that you omitted in your post? Could you post the full problem exactly as it is stated?

3. Yeah, I don't see any way to get that answer based on the problem you have.

This is about as far as you can get:

$\displaystyle \frac{5x^2y^2(a+b)}{2m^3n(d^2+d)}$

There is nothing to cancel. Sure you have the problem written correctly? Is there supposed to be an = in between these maybe?

4. ## Duh

No wonder I can't find the answer.

When I copied the problems from the book, I took the first fraction from #6 and took the second fraction from #7 and combined them. Here is the problem as it appears in my book:

$\displaystyle \frac{x^2y^2}{m^3n} * \frac{m}{x^3}$

Here I factor it:
$\displaystyle \frac{x*x*y*y}{m*m*m*n} * \frac{m}{x*x*x}$

And when I cancel the common factors I get:
$\displaystyle \frac{y^2}{m^2nx}$

I don't have a problem multiplying fractions, I just have a problem with reading things correctly.