The given details are,
Mohan can mow a lawn in 9 hours.
Work done by Mohan in 1 hour = 1/9
Mohan and Sohan can mow the lawn together in = 4 hours
Work done by Mohan and Sohan together in 1 hour = 1/4
We know that,
Work done by Sohan in 1 hour = (work done by together in 1 hour) – (work done by Mohan in 1 hr)
= 1/4 – 1/9
= (9-4)/36 (by taking LCM for 4 and 9 which is 36)
= 5/36
∴ Time taken by Sohan to complete the work = 1/(5/36) = 36/5hours.
