how many kg of pure salt must be added to 100 kg of 10 % solution of salt and water to increase it to a 20 % solution ?
"amount salt in 100 kg solution = 10 * 100 / 100 = 10 kg let x kg of pure salt be added then ( 10 + x ) / ( 100 + x ) = 20 / 100 100 + 10 x = 200 + 2 x 8 x = 100 x = 12.5 answer is d"
divide(subtract(20, 10), subtract(const_1, divide(20, 100)))