Thursday 23 February 2012

Work and time


12 people finish a work in 10 days then how long it takes for 15 people to finish the work. This problem can be solved using equations
People * days = different number of people * days required for them.
Deriving, people * days / diff number of people = days required 
From our previous example 12 * 10 = 15 * x,
12 * 10 / 15 = 8
Take the other problem if work is done by A in 12 days B in 4 days and C in 6 days, then together all of them how many days it take to finish the work?. Consider unit amount of work done by each and find the total
1/12 + 1/6 + ¼ = (1 + 2 + 3)/ 12 = 6/12 = ½
It is found that all of them together it takes 2 days to finish this work.
The other problem is solved by subtraction of unit work done by each. Take A& B together finishes a work in 4 days. This work can be done by A alone in 12days.Then how long it takes for B alone to finish this work?
            Both finish unit amount of work in ¼ days then B takes 1/4 – 1/12 = (3-1) / 12 =
2/12 = 1/6 i.e., 6days to finish this work.
And another problem, 5 people works for 7 hours to finish a work in 4 days, then a man if work for 10 hours, how long it takes to finish the work?
Again it is a game of equations
(5 * 7 * 4) / (1* 10) = 140/10 = 14
Our friend takes 14 days to finish the work!