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A silo (container for storing grain) is filled to capacity with p kilograms of wheat. Rats eat q kilograms a day. After 21 days, what percentage of the silo's capacity have the rats eaten?
Difficulty: Easy
A: 
\frac{21q}{30p}X100
B: 
\frac{q}{p}X100
C: 
\frac{21q-p}{p}X100
D: 
2100\left(\frac{q}{p}\right)