Please help solve these ratio problems

[roger12]

1. The problem statement, all variables and given/known data


In each of the following the properties of a compound are given. In each case find A:B:C

1. 3/8 of A with B and C 1:2

2. A, B, C are mixed according to the ratios A:B=1:7 and B:C=13:9

2. Relevant equations



3. The attempt at a solution

I just can't seem to solve these two. I got no idea where to even start. Please help.

[verty]

I'll help but show an attempt.

[daveb]

1. You know A is 3/8 of the compound, so how much is left over for B and C?

[roger12]

1. You know A is 3/8 of the compound, so how much is left over for B and C?

So that leaves 5/8 of B and C which are in the ratio 1:2.

Would then be:

3/8 of A, 5/8 of B and [ 5/8]/2 of C

?

[eumyang]

Would then be:

3/8 of A, 5/8 of B and [ 5/8]/2 of C

?

Not in the way I'm reading your problem. Does the numbers you have "assigned" for B and C, added together, give you 5/8? It does not.

If you have, say, X and Y in a ratio of 1:2, that means that X has to be 1/3 of the whole, while Y is 2/3 of the whole. Use this hint to figure out what fractions go with B and C if together they are 5/8 (of the compound).