EduGoog

Time & Work

If 40 men can build a wall 300 m long in 12 days working 6 hours a day, how long will it take 30 men to build a similar wall 200 m long working 8 hours a day ?

Option:
A. $4{1/2}$ days
B. 8 days
C. $10{1/2}$ days
D. 11 days
Answer: B . 8 days

Justification:

40 men can build 300 m long wall working 6 hour a day in = 12 days.
1 man can build 1 m long wall working 1 hour a day in = ${12 × 6 × 40} /300$
30 men can build 200 m long wall working 8 hour a day in = ${12 × 6 × 40 × 200}/{300 × 8 × 30}$ = 8 days.

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