Query Detail : SSC CGL Tier I

16 taps are fitted to a water tank. Some of them are water taps to fill the tank and the remaining are outlet taps used to empty the tank. Each water tap fills the tank in 6 hours. Each outlet taps can empty it in 18 hrs. On opening all the taps, the tank is filled in 1.5 hours. Find the number of inlet water taps? Answer: 7
Garima,   February 11th 2020,  
SSC CGL Tier I


Method 1:

Let no. of inlet tap = x so number of outlet tap = 16 - x

      Inlet                Outlet

           6                   18

Lcm = 18 L

eff      3            :           -1

So their 1 hr work = 3x + (-1) (16-x) = 18/1.5

3x - 16+x = 12

4x = 28

x = 7

Number of Inlet water taps = 7

Method 2:

x(1/6) - (16-x)/(1/18) = 1/1.5

{3x  -(16-x)}/18 = 1/1.5

{3x  -16 + x)}/18 = 1/1.5

4x - 16 = 12

4x = 28

x = 7

x =5