Maths-
General
Easy

Question

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

Hint:

Hint:
When two quantities of different units are compared and expressed as a ratio, it is known as Rate. For example, a car travels at a speed of 100 kilometres per hour, then it means in one hour it covers 100 kilometres.

The correct answer is: 7.2 hours


    Let’s say the area of the lawn is A.
    Step 1 of 3:
    It is given that Mohan takes 9 hours to mow a lawn of area A.
    Area of lawn mowed by Mohan in one hour = A over 9
    or we can say that the area that can be mowed by Mohan in one hour is A over 9.
    Step 2 of 3:
    Let’s say that Sohan can mow an area x in one hour. It is given that Mohan and Sohan together mowed the lawn in 4 hours.
    Area mowed by Mohan in 4 hours = 4 cross timesA over 9 = fraction numerator 4 A over denominator 9 end fraction
    Area mowed by Sohan in 4 hours = 4 cross times x = 4x
    Now, Area mowed by Mohan in 4 hours + Area mowed by Sohan in 4 hours = A
    fraction numerator 4 A over denominator 9 end fraction+ 4x = A
    x = fraction numerator 5 A over denominator 36 end fraction
    Step 3 of 3:
    So, Sohan can mow an area of fraction numerator 5 A over denominator 36 end fraction in one hour.
    Time taken by Sohan to mow the whole lawn = fraction numerator 1 over denominator fraction numerator 5 A over denominator 36 end fraction end fraction cross times A equals 36 over 5 equals 7.2 hours
    Final Answer:
    Hence, the time taken by Sohan to mow the lawn if he works alone is 7.2 hours

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