Question

if 3/5th of a water tank is filled in 3 min. how much more time will be required to fill the rest of the tank?

Answer 1

Given 3/5 of a water tank is filled in 3min
Then the ratio is 3/5:3
The rest of the water in tank = 1- 3/5 = 2/5
Let the time taken to fill 2/5 of the water tank be x
Then the ratio is = 2/5:x
⇒3/5:3 = 2/5:x 
product of extremes = product of means
⇒(3/5)×x = 3×2/5
⇒3x/5 = 6/5
⇒15x = 30
⇒x = 30/15
∴x = 2
∴Time taken to fill 2/5 th of the water tank is 2minutes

Answer 2

3/5 th of tank is filled 
total space left to fill is 2/5 th
time taken to fill 3/5= 3 minute
time taken to fill  1/5 th = 1 minute
time taken to fill other 2/5th part= 2 minute
∴ so it will require 2 minutes to fill rest of the tank i.e. 2/5 th of the tank.