I am mixing two components at a ratio of 7.5 parts A to one part B to make 200grams. How do I calculate A and B?

Question

I got 200 / 7.5 = 27B, then 200-27B = 173A

then tested it by: 27B / 173A and get 6.5 not 7.5

Am I doing this wrong?

Thanks in advance

Answer 1

Hello AJ,

One way to look at it is to:

1. count the total number of parts: 7.5 parts A + 1 part B = 8.5 TOTAL parts
2. divide 200 grams by the TOTAL parts to find how many grams are worth one (1) part: 200/8.5 = 23.53 grams
3. You are told that B has one part, and from the previous step, 1 part is worth about 23.53 grams. That means part B will be 23.53 grams
4. To find the mass of part A, you can then subtract 23.53 from 200: 200-23.53 = 176.47 grams. You could also have multiplied 23.53 by 7.5 (because, remember A has 7.5 parts) and you would have gotten the same thing.

Solution Check: A/B = 176.47/23.53 = 7.5.

Recap: in the 200 grams, there are 176.47 grams of A and 23.53 grams of B