When Individual work is given & Asked to find group work
In these types of questions the time taken by two or more persons to complete a particular work (Individual) is given and asked to find the time taken to complete the same work when they are working together (group).
How to solve these types of questions? Lets see.
- Assume the total work (Any number, say 100).
- Divide the total work by individual work (this gives the per day work).
- Add the per day works.
- Divide total work with combined per day work.
- The resultant is the required answer.
NOTE: This method is also known as LCM method.
This concept will be cleared by the following example.
Q: A can do piece of work in 10 days and B can complete the same work in 15 days. If they decided to work together, in how many days the work will be completed?
(A) 5 days
(B) 6 days
(C) 8 days
(D) 11 days
(E) 16 days
Sol: A ----- 10 3
30
B ----- 15 2
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Sum = 5 (3+2)
Here 30 can be assumed as total work and 3 (= 30/10) and 2 (= 30/15) are per day work of A & B respectively.
Combined per day work = 3 + 2 = 5
Required answer = 30 / 5 = 6 days.
Here you can assume any number (60, 90, 120,150 etc) instead of 30 and calculate per day work accordingly.
Initially you may confuse to use this method. Practice a set of similar questions to to build command. This is so simple and easy concept to get the answer quickly.
Observations:
- The combined work cannot be more than the individual work, always. (Here it is 6 less than both 10 and 15).
NOTE: We can extend this concept to any number of persons.
Try this:
Q: A , B and C can complete a work in 10, 12 and 15 days respectively, while working alone. If they are working together, the work will be completed in how many days?
(A) 6 days
(B) 8 days
(C) 4 days
(D) 10 days
(E) None of these
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Take any standard book and start solving questions from this topic. Still you have any doubts post your comment.
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