If grapes are 92% water and raisins are 20% water by weight, then how much did a quantity of raisins, which currently weighs 10 pounds, weigh when all the raisins were grapes? (Assume that the only difference between their raisin-weight and their grape-weight is water that evaporated during their transformation.)

If grapes are 92% water and raisins are 20% water by weight, then how much did a quantity of raisins, which currently weighs 10 pounds, weigh when all the raisins were grapes? (Assume that the only difference between their raisin-weight and their grape-weight is water that evaporated during their transformation.)

a) 25 pounds

b) 46 pounds

c) 92 pounds

d) 100 pounds

e) 146 pounds

Since raisins are 20% water, the 10 pounds of raisins are composed of 2 pounds of water and 8 pounds of other stuff.

Since grapes are 92% water, the 8 pounds of other stuff must constitute 8% of the grapes:

8 = (8/100) x

x = 800/8 = 100.

The correct answer is D.