one pipe can fill a tank in 15 hour.but because of hole in a tank,this tank fill in 20 hour.so in how much time this hole will empty the full tank?	Choose the correct choice from the following answers.
A) 30	B) 40	C) 50	D) 60	E) 70
in 1 hour hole empty=[1/15-1/20]=1/60   so total time taken to empty the full tank through hole=60 hour.   answer 60
<result>D</result>
one pipe can fill a tank in 15 hour.but because of hole in a tank,this tank fill in 20 hour.so in how much time this hole will empty the full tank?