Sam can mow a lawn in 20 min, while takes 10 min longer to mow the same lawn. How long will they take to mow the lawn if they work together?

A 12 min
B 14 min
C 15 min
D more than 15 min

Correct Answer: 12 min

In 1 minute, Sam mows 1/20 of the lawn In 1 minute, Mark mows 1/(20 + 10) = 1/30 of the lawn (1/20 + 1/30) = 5/60 = 1/12 of the lawn takes 1 minute So, whole(1) lawn takes 12 minutes
Bissoy MCQ
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