How many kg of pure salt must be added to 100kg of 10% solution of salt and water to increase it to a 25% solution?  Select
A) 6.7 B) 1.3 C) 9.6 D) 20 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 ) = 25 / 100 40 + 4 x = 100 + x 3 x = 60 x = 20 answer is d"
Answer: D