How many kg of pure salt must be added to 100kg of 10% solution of salt and water to increase it to a 35% solution?
Choose the correct choice from the following answers
A) 6.7  B) 38.5  C) 9.6  D) 12.5  E) 7.9

Rationale: "amount salt in 100 kg solution = 10 * 100 / 100 = 10 kg let x kg of pure salt be added then ( 10 + x ) / ( 100 + x ) = 35 / 100 200 + 20 x = 700 + 7 x 13 x = 500 x = 28.5 answer is b"
Answer: B