7 men can dig a canal in 14 weeks. After 2 weeks of work, they are joined by another 7 men. In how many weeks more is the work finished?
The Usual Method
If 7 men can dig a canal in 14 weeks, than 7 men can dig th of the canal in 1 week. Since, 7 men work for 2 weeks, or th of the canal is dug. Hence, amount of work remaining = .
Additional 7 men join, so now it becomes 14 men. If 7 men dig a canal in 14weeks, 14 men will take 7 weeks to dig the canal. Hence, th of the canal will be dug by 14 men in 1 week.
Since it takes 1 week to do of the work, to do of the work, it will take 6 weeks.
Estimated Time to arrive at the answer = 45 seconds.
Since, the 7 men work for 2 weeks, balance work is equivalent of 14 – 2 = 12 weeks. However, now since 7 more men join, the capacity doubles up and so time required halves. Hence, time taken will be half of 12 weeks = 6 weeks.
Estimated Time to arrive at the answer = 10 seconds.