Question

In a mixture of concrete, there are two lb of cement mix for each pound of gravel. If the mixture contains a total of 120 lb of these two ingredients, how many pounds of gravel are there?

Answer 1

The total pounds in a simple mixture is 3, where 2 are cement and 1 is gravel.

So for cement: \[
\frac{2}{3}=\frac c{120}
\]And for gravel: \[
\frac 13=\frac g{120}
\]

Answer 2

What do I do next? To solve

Answer 3

@wio

Answer 4

cross multiply

Answer 5

solve for each

Answer 6

I haven't crossed multiplied since freshman year. So, I got 80 for the cement and 40 for gravel. What do I do next?

Answer 7

http://www.wolframalpha.com/input/?i=2%2F3%3Dc%2F120%2C+1%2F3%3Dg%2F120

That is correct.

Answer 8

That's it?

Answer 9

Yes. It just asks for the pounds of gravel.