Question

A piece of gold-aluminium alloy weighs 49N when suspended from a spring balance and submerged in water it weighs 39.2N what is the weight of Gold in the alloy if the specific gravity of gold is 19.3 and aluminium is 2.5?

Answer 1

specific gravity = 49 / (49 - 39.2)

(x * 19.3) + [(1 - x) * 2.5] = specific gravity

x is the fraction of the alloy that is gold

Answer 2

19.3 + 2.5 = 21.8.

19.3/21.8*49 = 43.4 N. of gold.
49-43.4 = 5.6 N. of of aluminum.