RRB NTPC 17 January 2017 Paper

Question : 23 of 120

Marks: +1, -0

A water tank has two holes. The 1” hole alone empties the tank in 9 minutes and 2nd hole alone empties the tank in 6 minutes. If water leaks out at a constant rate, how many minutes does it take if both the holes together empty the tank ?

3 $3/5$
$3 /5$
1 $3/ 5$
2 $3 /3$

Validate

Solution:

(1) Time taken by 1st hole to empty the tank alone = 9 min
Time taken by 2nd hole to empty the tank alone = 6 min
Let the total work = LCM (9, 6) = 18units
Work done by 1st hole in one minute =

18/9

= 2 units
Work done by 2nd hole in one minute =

18/6

= 3 units
Hence, work completed by both holes working together in one minute = 2+3 = 5 units
Since total work = 18 units
Both will take time =

18/5

3/5

minutes

Go to Question:

Prev Question

Next Question