CAT Exam Numerical Ability Time and Work

Two pipes a and b fill a tank in 15 hrs and 20 hrs respectively. while a third pipe c can empty the full tank in 25hrs. all the three pipes are opened in the beginning. after 10hrs,c is closed. in how much time, will the tank be full?

Read Solution (Total 3)

a's 1 hr work = 1/15
b's 1 hr work = 1/20
c's 1 hr work = 1/25

In 1 hr, d tank filled ll be
1/15 + 1/20 - 1/25 = 20+15-12/300 = 23/300

In 10 hrs , 10 * 23/300 = 23/30
Remaining part = 1 - 23/30 = 7/30

c is closed,,, a+b is opened...
a+b's 1 hr work = 1/15 + 1/20 = 35/300 = 7/60

a+b ll fill
1 hr -- 7/60
x ---- 7/30

x = 7/30 * 60/7 = 2hrs

The tank ll be filled in 10 + 2 = 12hrs

Ans : 12 hrs
10 years agoHelpfull: Yes(9) No(0)

10(1/15 + 1/20 - 1/25(since it is emptying))=23/30
remaing is 1- 23/30= 7/30
let no.of hrs be x...
x(1/15 + 1/20)=7/30
7x/60=7/30
x=2hrs
9 years agoHelpfull: Yes(0) No(0)
SARASWATHY IS COORECT
12 HRS
7 years agoHelpfull: Yes(0) No(1)

CAT Other Question

Two pipes can fill a tank in 15hr and 12hr respectively while a third pipe can empty it in 20hrs.if the tank is empty and all the three pipes are opened the tank will be full in 2 taps can fill a tank in 8hrs and 6hrs respectively a 3rd tap can empty it in 12hrs. how long will it take to fill the tank if all 3 taps are opened together?