RRB Group-D Model Paper 20 with answers for online practice

Given:
A can fill the tank = 4 hours
B can empty the tank = 6 hours
Concept used:
Total capacity = LCM
Filled tank in unit value of time is known as efficiency
The efficiency of inlet pipes is positive
The efficiency of outlet pipes is negative
Formula used:
Efficiency = total capacity/total time
Calculations:
Let the total capacity of the tank be x
The efficiency of A = x/4
The efficiency of B = -x/6
The total efficiency of A and B together = (x/4) – (x/6)
⇒ (3x – 2x)/12
⇒ x/12
Total time is taken by A and B to fill the whole tank = x/(x/12)
⇒ 12 hours
∴ Total time is taken by A and B to fill the whole tank = 12 hours