Question
Quantitative Aptitude Question on Time and Work
Humans and robots can both perform a job but at different efficiencies. Fifteen humans and five robots working together take thirty days to finish the job, whereas five humans and fifteen robots working together take sixty days to finish it. How many days will fifteen humans working together (without any robot) take to finish it?
A
36
B
32
C
45
D
40
Answer
32
Explanation
Solution
The correct answer is (B):
Let the rates of work of each human and each robot be H and R respectively (both in units/day).
15H+5R = 1/30 ...(1)
5H+15R = 1/60 ....(2)
3(1)-(2) ⇒40H = 1/12
H= 1/480
In a day, 15 humans can complete 15H i.e. 1/32th of the job.
15 humans can complete the job in 32 days.