5 skilled workers can build a wall in 20 days; 8 semi-skilled workers can build a wall in 25 days; 10 unskilled workers ...

Question

5 skilled workers can build a wall in 20 days; 8 semi-skilled workers can build a wall in 25 days; 10 unskilled workers can build a wall in 30 days. If a team has 2 skilled, 6 semi-skilled and 5 unskilled workers, how long will the team take to build the wall?

A. 20 days
B. 18 days
C. 16 days
D. 15 days

Accepted Answer

The team of 2 skilled, 6 semi-skilled and 5 unskilled workers will take 15 days to build the wall. This is a classic work-rate problem. First find the individual rate of one worker of each type per day, then combine the rates of all workers in the mixed team. The total rate tells how many walls per day the team builds, and the reciprocal gives the number of days for one wall.