patnaiksonal wrote:
One pipe can fill a tank in 1 hour, while another pipe can fill the same tank in 2 hours. How long will it take to fill the tank if both pipes are used together?
A 2/3 hour
B 1/3 hour
C 1 hour
D 4/5 hour
E 3/4 hour
Another approach is to assign a "nice" value to the volume of the tank (a value that works with 1 hour and 2 hours)
Let's say the tank contains
6 gallons of water
One pipe can fill a tank in 1 hourSo it can fill
6 gallons in 1 hour.
In other words, this pipe's RATE =
6 gallons per hour
Another pipe can fill the same tank in 2 hoursIf this pipe can pump
6 gallons in 2 hours, its RATE =
3 gallons per hour
How long will it take to fill the tank if both pipes are used together?The COMBINED RATE of the two pipes =
6 +
3 =
9 gallons per hour
Time =
output/
rate=
6/
9 hours
= 2/3 hours
Answer: A
Cheers,
Brent