If after 100 grams of water were added to the 20%-solution of alcohol, the strength of the solution decreased by one-fourth, how much of the 20%-solution was used?
Select:
A) 300
B) 250
C) 150
D) 200
E) 210
The 20% alcohol solution decreases by 1/4 once the 100 grams of water is added so  100/.05= 
<gadget id="calculator"> 100/.05</gadget>
<output>2_000</output>
2000*.15% (3/4 of 20%) is 300 grams.   answer is 300
<result>A</result>
If after 100 grams of water were added to the 20%-solution of alcohol, the strength of the solution decreased by one-fourth, how much of the 20%-solution was used?