A can finish a work in 36 months, B in 18 months and C in 24 months. B and C start the work but are forced to leave after 4 months. The remaining work was done by A in 22 months.
24 months
A`s 1 month`s work = 136
B`s 1 month`s work = 118
C`s 1 month`s work = 124
(B + C)`s 1 month`s work
= 118+124=772 [LCM of 18 and 24 = 72]
Work done by B and C in 4 months = 772×4=718
Remaining work = 1−718=18−718=1118
Now, 136 work is done by A in 1 month
So, 1118 work is done by A in 36×1118=22 months
So, the remaining work was done by A in 22 months.