Question

An alloy is 70% iron. How much of this alloy do you need if you want to obtain 50 7/20 lb of iron?

Answer 1

72 lb

Explanation:

An alloy is 70% iron, that is, there are 70 lb or iron every 100 lb of the alloy. This is our conversion factor. In order to find out how much allow is required to obtain 50 7/20 lb (50.35 lb) of iron, we will use proportions.

50.35 lb iron × (100 lb alloy/70 lb iron) = 72 lb alloy

We will need 72 lb of the alloy.

Answer 2

Use proportions. X is what you want.

70 50.35lb
__ = _____

100 x

Cross multiply to get 70x = 5035
Solve to get about 71.93 lbs of the alloy.