Question

Five liters of 31.2% acid solution has to be made out of a 40% and a 18% acid solution. How many litres of each of the 40% and 18% solution need to be mixed?

• A. 4 and 5
• B. 3 and 2
• C. 5 and 4
• D. 2 and 3

Answer 1

The correct option is B

3 and 2

Let x lt of the 40% and y lt of the 18% solution be mixed.

That is, we have, x + y = 5…(i)

and 0.40 x + .18y = 0.312 (5)

i.e 40x + 18y = 156……(ii)

Multiplying (i) by (-18) , we have

-18 x - 18 y = - 90…..(iii)

Adding , (ii) and (iii) , we get