Question

21 workers working 5hours a day for 30 days can build a platform of width 150 meters, length 20 meters and height 15 meter. How many days will 24 workers working 7 hours a day will take if they have to build a platform of width 720meter, length 15 meter and height 10 meters?

Type the answer in the blank below:
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Answer 1

Solution:
Equate the amount of work in terms of man - hours and volume of the platform.

21 workers, 5 hours a day, 30 days = $150\times 20\times 15$

24 workers, 7 hours a day, N days = $720\times 15\times 10$

Taking the ratio ,$\frac{21\times 5\times 30}{24\times 7\times N}=\frac{150\times 20\times 15}{720\times 15\times 10}$

N =45