M4maths Previous Puzzles

18 Jun 2019 Pipe

A tap can fill a tank in 30 minutes another tap can empty it in 1.5 hours. if both the taps are opened at 11.40 am. then at what time will the tank be filled?

OPtion

1) 1:00 PM
2) 12:25 PM
3) 1:25 PM
4) 12:45 PM
5) 1:30 PM
6) 12:50 PM
7) 1:15 PM
8) 12:35 PM
9) 1:20 PM
10) None of these

Solution

1 min. filling =1/30
1 min. empty=1/(1.5*60)
In 1 min. tank will be filled (1/30)-[1/(1.5*60)] = 1/30 - 1/90 = (3-1)/90 = 1/45
So tank will completely filled in 45 min. from the start
So 11:40 + 45 min = 12:25 PM

Correct Option: 2 Best Solution (0)