Tips and Tricks on Time and Work: (Shortcut Methods)
Before going to solve the time and work problems . We need to understand the relation between Time, Work and Manpower (men, women, person, boy , girl etc.,).
Work α MDT [M=Men, D=Days, T=Time]
1) W1 / W2 = M1D1T1/M2D2T2 .
2) If W1=W2 Then M1D1T1= M2D2T2.
3) M1D1 / W1 = M2D2 / W2 Here, Time is constant(same)
4)M1D1T1E1W2 = M2D2T2E2W1 (E1, E2 are efficiency of the persons in two groups)
Practice Questions on Time and Work:
A takes 10 days to complete a work and B takes 5 days to complete the same work. Then, How many days A and B completes the work if they work together?
Sol: A B
10 days 5 days
Let us assume, Total Work= LCM(10,5)=10 units.
A’s 1day work=10 units/10= 1 unit.
B’s 1day work=10 units/5 = 2 units.
(A+B)’s 1 day work= (1+2)units
= 3 units
(A+B) total work can be done in Total Work/1day work.
=>10 uits/3units =10/3days.
If we understand the logic in this method, It become very simple to solve other hard problems also in less time.
A->20 days and B->25 days Then, (A+B)= ? days.
Sol: Total Work = LCM(20,25) =100 units.
A’s 1day Work = 100/20 = 5 units
B’s 1 day work = 100/25 = 4 units
(A+B)’s 1 day work = (5+4) = 9 units
(A+B)’s Total work can be done in Total Work/1 day work=100/9 units
= 11.11 days. 11 days(approx).
Note: No need to write all these steps .For understanding purpose, I have written here.
A->5days, B->7 days, C->9days Then, (A+B+C)=? Days.
Sol: T.W= LCM(5,7,9)=(5*7*9 )units
A= (7*9) units
B= (5*9) units
C= (5*7) units
(A+B+C)’s 1 day work= (7*9)+ (5*9) + (5*7)
(A+B+C)’s completes the work in [(5*7*9 )/ 143 ] days.
TIME & WORK Practice Problems with answers: