If grapes are 91% water and raisins are 19% water, then how many kilograms did a quantity of raisins, which currently weighs 9 kilograms, 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.)  Select.
A) 63
B) 72
C) 81
D) 90
E) 99
Let x be the original weight.   The weight of the grape pulp was 0.09x.   Since the grape pulp is 81% of the raisins, 0.09x = 0.81(9 kg).   Then x = 9*9= 
<gadget id="calculator">9*9</gadget>
<output>81</output>
81 kg.   The answer is 81.
<result>C</result>
If grapes are 91% water and raisins are 19% water, then how many kilograms did a quantity of raisins, which currently weighs 9 kilograms, 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.)