How many pounds of salt at 50 cents/lb must be mixed with 40 lbs of salt that costs 25 cents/lb so that a merchant will get 20% profit by selling the mixture at 48 cents/lb? Choose the correct choice from the following options:
A) 20
B) 15
C) 40
D) 60
E) 25

Rationale: "selling price is 48 cents / lb for a 20 % profit , cost price should be 40 cents / lb ( cp * 6 / 5 = 48 ) basically , you need to mix 25 cents / lb ( salt 1 ) with 50 cents / lb ( salt 2 ) to get a mixture costing 40 cents / lb ( salt avg ) weight of salt 1 / weight of salt 2 = ( salt 2 - saltavg ) / ( saltavg - salt 1 ) = ( 50 - 40 ) / ( 40 - 25 ) = 2 / 3 we know that weight of salt 1 is 40 lbs . weight of salt 2 must be 60 lbs . answer ( d )"
Answer: D