in this chapter one this we should remember i.e. admits means we should use ‘+’ sign and empty means we should use ‘-‘ sign?

**Problem 1:** Two pipes A and B can fill a tank in 20 min and 30 min respectively. If both pipes are opened together, the time taken to fill the tank is?

Solution:

A———> 20 +3

L.C.M 60

B———–>30 +2

3+2=5

**Problem 2:** A pipe can fill a tank with water in 3 hours. Due to leakage in the bottom, it takes hours to fill it. in what time the leak will empty the fully filled tank?

Solution:

A———–> 3hrs

L.CM

A+B———-> 3

A+B=3

B=3-

hrs

Shortcut: =

**Problem 3:** A cistern is normally filled in 9 hours but due to the leak in the bottom, it takes one hour more to be filled. if the cistern is full, in what time will the leak empty it?

Solution:

A———>9 10

L.C.M 90

A+B—–>10 9

A+B=9

B=9-10

B=-1

Shortcut: =