J completed a piece of work in 7 days, working 4 hours in a day while K completed a piece of work in 5 days working 7 hours in a day. In how many days can they together complete double of the work working 14 hours a day?
J completed a piece of work in 7 days, working 4 hours in a day while K completed a piece of work in 5 days working 7 hours in a day. In how many days can they together complete double of the work working 14 hours a day? Correct Answer 20/9 days
Given:
J completed a piece of work in 7 days, working 4 hours day.
K completed a piece of work in 5 days working 7 hours a day.
J and K together worked for 14 hours a day.
Concepts used:
1 day's work done by an individual = Work/time
Time = Work/Efficiency
Calculation:
Time taken by J to complete the work in hours = 7 × 4 = 28 hours
Time taken by K to complete the work in hours = 7 × 5 = 35 hours
1 hour work done by individual = Work/time
⇒ 1 hour work of J = 1/(7 × 4) = 1/28
⇒ 1 hour work of K = 1/(5 × 7) = 1/35
⇒ 1 day, 1 hour work of J and K = (1/28) + (1/35) = 9/140
1 day, 14 hours work of J and K = 14 × 9/140 = 9/10
Time = Work/Efficiency
Time taken by J and K in completing twice the full work = 2/(9/10) days = 20/9 days
∴ Working 14 hours a day, J and K took 20/9 days in completing double the piece of work.