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RD Sharma Solutions Class 8 Mathematics Solutions for Time and Work Exercise 11.1 in Chapter 11 - Time and Work

Question 4 Time and Work Exercise 11.1

Mohan takes 9 hours to mow a large lawn. He and Sohan together can mow in 4hours. How long will Sohan take to mow the lawn if he works alone?

Answer:

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.

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