If machine A and B can produce 1100 units in 9 h and 12 h respectively. In how many hours can machine A and B working together at these constant rates produce 1100 units?
Show answer & explanation
Correct answer: A
Explanation
The correct answer is option 1 i.e. (36/7)
Machine A can produce 1100 units in 9 hours.
Machine B can produce 1100 units in 12 hours.
Work rate = Amount of work done per unit of time
Work rate of machine A = Total work/Total time = 1100/9 = 122.22 units/hr
Work rate of machine B = Total work/Total time = 1100/12 = 91.67 units/hr
Combined work rate = Work rate of machine A + Work rate of machine B = 122.22 + 91.67 = 213.89 units/hr
Time = Total work/Combined work rate = 1100/213.89 = 36/7 hr