Question

A can do a piece of work in 18 days,B in 27 days &C in 36 days.they start working together but only C work till the completion.A leaves 7 days & B leaves 8 days before the completion of work.The whole work was completed in

Answer 1

Well the method is just same.

You can do it by this method:

Let the work be completed in x days. C work for x days then A works for (x-8) days and B works for (x-12) days.

According to the question,

[(x-8)/36 + (x-12)/54 + x/72] = 1;

[(6x-48+4x-48+3x)/216] = 1;

13x-96 = 216;

13x = 216+96 = 312;

x = 312/13 = 24 days.

Alternatively, We can solve it through percentage method:

Let the work be completed in X days. C works for X days then A works for (X-8) days and B works for (X-12) days.

% of work completed by A in one day = 100/36 = 2.78%

% of work done by B in one day = 100/54 = 1.85%

% of work done by C in one day = 100/72 = 1.38%

total work = 100%

(X-8)*2.78+(X-12)*1.85+1.38X = 100

2.78X+1.85X+1.38X-45 = 100

6.1X = 145

hence, X = 145

^_^

Hope it will help u.