Question

a compound of 100 litre contains acid and water in the ratio 3 :2. How much acid to be added to get the ratio 3:l?

Answer 1

75 litre acid should be added

Answer 2

The acid-to-water ratio of the compound is 3:2, so:

• 3x + 2x = 100
• 5x = 100
• x = 20

Now that we have solved for x, lets find the amount of acid and water in the compound:

• 3 (20) = 60 liters of acid
• 2 (20) = 40 liters of water

If we wanted the ratio of acid and water to be 3:1, then:

• 3x + x = 4x

Since we already have 40 liters of water and you can't remove stuff from the compound, we should use 40 as x. (3:1 means three parts of acid to one part of water, so the amount of water doesn't need to change)

• 3 (40) + 40 = 160
• 120 + 40 = 160

So the new compound has 120 liters of acid and 40 liters of water, and has the ratio 3:1. The amount of acid that should be added is:

• 120 - 60 = 60 liters of acid should be added.