4 junior labourers can complete the house in 60 days while 8 senior labourers can complete same house in 20 days. In how many days can 6 junior and 4 senior labourers complete the house if they work together?
4 junior labourers can complete the house in 60 days while 8 senior labourers can complete same house in 20 days. In how many days can 6 junior and 4 senior labourers complete the house if they work together? Correct Answer 20 days
Given:
4 junior labourers can complete the house in 60 days.
8 senior labourers can complete same house in 20 days.
Concepts used:
1 day work done by individual = Work/time
Time = Work/Efficiency
Calculation:
1 day work done by individual = Work/time
1 day work of 1 junior labourer = 1/(4 × 60) = 1/240
⇒ 1 day work of 6 junior labourers = 6/240 = 1/40
1 day work of 1 senior labourer = 1/(8 × 20) = 1/160
⇒ 1 day work of 4 senior labourers = 4/160 = 1/40
⇒ 1 day work of 6 junior and 4 senior labourers together = (1/40) + (1/40) = 1/20
Time = Work/Efficiency
⇒ Time taken by 6 junior and 4 senior labourers to complete work together = 1/(1/20) days = 20 days
∴ 6 junior and 4 senior labourers can complete the house in 20 days.