An acid solution contains 40% acid, what quantity of solution is to be replaced by the acid to make it 50% acid solution?

Let the amount of acid solution to be replaced is x lit and original solution is 100 lit.

So we replace x lit of acid solution, we have now 100 - x lit of solution. 

The acid content is 40 - 0.4x, and we add x lit of acid, hence, 

40 - 0.4x + x is the new acid content, but it's now 50%.

40 - 0.4x + x = 50

x = 100/6 lit = 16.6 lit.

16.6 lit of acid solution is to be replaced by the acid.

Regards,

Team,

TopperLearning.