You have two small sculptures made of copper and gold. The first sculpture has 5% gold while the second one has 10% gold. The first sculpture has twice the mass of the second one. You melt both, extract the gold and you make a ring of pure gold that is 10 g. What is the mass of the lighter sculpture?
a. 40g
b. 50g
c. 80g
d. 100g
e. 150g

Option b. 50g.

Explanation:

We have:

m₁ = is the first sculpture = 5/100 = 0.05

m₂ = is the second sculpture = 10/100 = 0.10

Since the first sculpture has twice the mass of the second one:

    (1)  

And, when we melt both sculptures, the ring obtained has 10g:

 (2)

Hence, we have two equations and two variables. By equating equation (1) with (2) we can find the mass of the lighter sculpture:

Hence, m₁ is:

Therefore, the correct option is b: 50 g is the mass of the lighter sculpture.      

I hope it helps you!

this could be newton#'s law of cooling. the cooling curve is exponential