Question

50kg of an alloy of Pb and Sn contains 60% of lead. how much lead must be melted to make an alloy containing 75% of lead?

Answer 1

Answer:

50 kg of an alloy of lead and tin contains 60% of lead.

50 kg of alloy contains 60%

60% of 50 kg = 30 kgs of lead.

How much lead must be melted into it to make the alloy contain 75% of the lead

Let we add x kgs of lead

Thus total total weight of alloy will be = 50 + x kg

The weight of lead will increase to 30 + x kg

This will be 75% of total weight of alloy

75% = 75/100 = 0.75

Thus 30 + x = 0.75 (50 + x)

30 + x = 37.5 + 0.75x

x - 0.75x = 37.5 - 30

0.25 x = 7.5

x = 7.5/0.25

x = 30

Thus 30 kg lead to be added to make the alloy contain 75% of the lead