A contractor agreeing to finish a work in 150 days, employed 75 men each…
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A contractor agreeing to finish a work in 150 days, employed 75 men each working 8 hours daily. After 90 days, only 2/7 of the work was completed. Increasing the number of men by _____ and each one is working now for 10 hours daily, the work can be completed in time.
- A.
75
- B.
225
- C.
150
- D.
100
Attempted by 34 students.
Show answer & explanation
Correct answer: C
Solution: 3
Total hours worked by 75 men = 90 × 8 = 720
Man-hours put in = 720 × 75 = 54000 man-hours
In so many man-hours, 2/7 of the work is completed
Fraction of work left = 1-2/7 = 5/7
This will take = {54000 × (5/7)}/(2/7) = 135000 man-hours
∵ No. of hours to be worked for remaining days = 60 × 10 = 600
∴ No. of men to be employed = 135000 ÷ 600 = 225
∴ Additional men to be employed = 225 - 75 = 150
Short Trick
We know, (Men1 × Days1 × Hours1)/work1 = (Men2 × Days2 × Hours2)/work2
⇒ (75 × 90 × 8)/(2/7) = (n × 60 × 10)/(5/7)
⇒ n = 225
Hence, increase in number of men = 225 - 75 = 150