Question

Bronze which costs $7.05/kg is made by

combining copper which costs $6.20/kg with
tin which costs $8.70/kg. Find the number of
kg of copper and tin required to make 5 kg of
bronze.
Find the number of kg of copper and tin required to make 15.3 kg of bronze. (NO LINKS)

Answer 1

Answer: 3.3 kg of Cu, 1.7kg of Sn

I abbreviate copper as Cu and tin as Sn.

Explanation:

For 5 kg of $7.05$/kg bronze: Let x be the mass of Cu. The mass of Sn would be 5-x.

Multiply these two masses by their respective element cost.

Cu = ($6.20/kg)x [The total value of copper in 5 kg of bronze]

Sn = ($8.70/kg)(5-x) [The total value of tin in 5 kg of bronze]

We know that:

($6.20/kg)x + ($8.70/kg)(5-x) = $7.05

Solve for x. I get

x= 3.3 kg of Cu

5-x = 1.7kg of Sn

==

Check the result for 5 kg of bronze:

(3.3 kg of Cu)*($6.20/kg) = $20.46 cost of Cu

(1.7kg of Sn)*($8.70/kg) = $14.79 cost of Sn

Thus, the total cost for 5kg of bronze is $35.25. That makes it $7.05/kg.