Question

Determine how much copper and how much
zinc is needed to make a 99 kg brass ingot if
they have to be in the proportions copper :
zinc: :8 : 3 by mass.

Answer 1

99kg total mass in the ratio 8:3 copper:zinc units

let's add 8 + 3 to get 11 total units
so we have 8 copper/11 total units, we have (8/11)*99 = 72kg copper

to determine zinc, you can simply subtract 99kg - 72 kg to get the zinc