Question

A foundry has been commissioned to make souvenir coins. The coins are to be made from an alloy that is 40% silver. The foundry has on hand two alloys, one with 50% silver content and one with a 25% silver content. How many kilograms of each alloy should be used to make 35 kilograms of the 40% silver alloy?

Answer 1

The ratio of 50% content to 25% content is
.. (40-25) : (50-40) = 15:10 = 3:2
There is a total of 5 "ratio units" in this ratio, so each is representing 35 kg/5 = 7 kg of alloy.

21 kg of 50% alloy and 14 kg of 25% alloy should be used.