One solution contains 15%acid,while another solution contains 20% acid.How much of the solution is needed to make 100ml of solution that is 18% acid?

Solution:

We need solution containing 15%acid : x

We need solution containing 18%acid : y

x + y =100

0.15x + 0.2y = 0.18*100

x= 40

y= 60

So

We need solution containing 15%acid : 40 ml

We need solution containing 18%acid : 60 ml