Question

How much salt must be added to 60 kg of a 20% solution of salt to increase it to a 40%solution of salt

Answer 1

for short trick:required salt=60*(40-20)/(100-40)=20kg.

for explanation:in 60kg, 20% is salt i.e. 60*20/100=12kg
for being 40% the ratio would be (12+x)/(60+x)=40/100 where x is the required amount on solving the aove equation we get x=20kg.

Answer 2

Answer is in the attachment

Hope it helps!!