Question

A mixture of 40 litres of milk an d water contains 10% water. How much water should be added, so water may be 20% in the new mixture?

Answer 1

in 40 lit water contains 4 lit (10%)
milk contains 36 lit
let x lit should be added
(4+x)/40+x)=1/5
20+5x=40+x
4x=20
x=5lit
so 5 lit of water should be added
hope u got it if doubt ask