Basic Concepts of Time and Work
Most of the aptitude questions on time and work can be solved if you know the basic correlation between time, work and man-hours which you have learnt in your high school class.
- Analogy between problems on time and work to time, distance and speed:
- Speed is equivalent to rate at which work is done
- Distance travelled is equivalent to work done.
- Time to travel distance is equivalent to time to do work.
- Man – Work – Hour Formula:
- More men can do more work.
- More work means more time required to do work.
- More men can do more work in less time.
- men can do a piece of work in hours, then
Part of work done by for days = .
can do a piece of work in days, then ‘s 1 day’s work = .
- If ‘s 1 day’s work = , then can finish the work in days.
Where,M = Number of men
D = Number of days
H = Number of hours per day
W = Amount of work
is times as good a workman as , then:
- Ratio of work done by and =
- Ratio of times taken by and to finish a work = i.e.; will take of the time taken by to do the same work.
Shortcuts for frequently asked time and work problems
and can do a piece of work in days and days respectively, then working together:
- They will complete the work in days
- In one day, they will finish part of work.
and together can do a piece of work in days, and together can do it in days and and together can do it in days, then number of days required to do the same work:
- If A, B, and C working together =
- If A working alone =
- If B working alone =
- If C working alone =
If alone does the work and takes days more than and working together.
If alone does the work and takes days more than and working together.Then,
and can together complete a job in days.
- If Dm1b1/(m2b1+m1b2)days. men or boys can complete a work in days, then men and boys can complete the same work in
- If Dmwb/(mw+wb+bm) days men or women or boys can do work in days, then 1 man, 1 woman and 1 boy together can together do the same work in
- If the number of men to do a job is changed in the ratio , then the time required to do the work will be changed in the inverse ratio. ie;
- If people work for same number of days, ratio in which the total money earned has to be shared is the ratio of work done per day by each one of them.
, , can do a piece of work in , , days respectively. The ratio in which the amount earned should be shared is
- If people work for different number of days, ratio in which the total money earned has to be shared is the ratio of work done by each one of them.