20 hrs

23 hrs

30 hrs

21 hrs

D. 21 hrs

work done by the leak in 1 hour=(1/3)-(1/(7/2))=(1/3)-(2/7)=(1/21).

The leak will empty .the tank in 21 hours.

18 hrs

13 hrs

20 hrs

23 hrs

39 min

40 min

50 min

45min

20 hrs

23 hrs

30 hrs

21 hrs

7 hrs

7 hrs 30 min

5 hrs

5 hrs 30 min

100 hrs

122 hrs

177 hrs

112 hrs

10 min

20 min

40 min

50 min