Question

3. Metal is made using Copper, zine and lead in the ratio 13:6:1, the mass of the zinc is 90kg, calculate

1) the total mass of metal
2) the mass of the copper
3) the mass of the lead as a % of the total mass of the metal​

Answer 1

1) 150 kg

2) 97.5 kg

3) 5%

Explanation:

Ratios of each metal to total mass of metal can be computed by dividing its corresponding value by the sum of all the values in the ratio

The ratio of zinc to metal = 6/(13 + 6 + 1) = 6/20 = 3/10

Let the total mass of the metal be X

Then mass of zinc = (3/5)X = 90 kg (given)

1) Multiplying both sides by 5/3 gives X = 5/3 x 90 = 150 kg which is the total mass of metal

2) Ratio of copper to metal mass = 13/20
Mass of copper = 13/20 x 150 = 97.5 kg

3) Mass of lead as a ratio of metal = 1/20 = 0.05

As percentage, multiply by 100 to get 0.05 x 100 = 5%