15
experts can do as much work as a 5 Trainee in
given time. A piece of work is to be done by
8 experts and 15 trainees. How many traines
alongside trainess would one need to complete
a similar work in some duration of time?
Answers
Answer:
STEP 1: Calculate how much work each person/machine does in one unit of time (could be days, hours, minutes, etc).
How do we do this? Simple. If we are given that A completes a certain amount of work in X hours, simply reciprocate the number of hours to get the per hour work. Thus in one hour, A would complete of the work. But what is the logic behind this? Let me explain with the help of an example.
Assume we are given that Jack paints a wall in 5 hours. This means that in every hour, he completes a fraction of the work so that at the end of 5 hours, the fraction of work he has completed will become 1 (that means he has completed the task).
Thus, if in 5 hours the fraction of work completed is 1, then in 1 hour, the fraction of work completed will be (1*1)/5
STEP 2: Add up the amount of work done by each person/machine in that one unit of time.
This would give us the total amount of work completed by both of them in one hour. For example, if A completes of the work in one hour and B completes of the work in one hour, then TOGETHER, they can complete of the work in one hour.
STEP 3: Calculate total amount of time taken for work to be completed when all persons/machines are working together.
The logic is similar to one we used in STEP 1, the only difference being that we use it in reverse order. Suppose . This means that in one hour, A and B working together will complete of the work. Therefore, working together, they will complete the work in Z hours.