40 workers can build 40 engines working 6 hours a day. How many workers need to be appointed extra to boost the production to double if they work 8 hours a days?

Question: 40 workers can build 40 engines working 6 hours a day. How many workers need to be appointed extra to boost the production to double if they work 8 hours a days?Solution: 6 hours to build 40 engines by 40 workers 1 hour to build 1 engine by = (40 × 6)/40 workers 8 hours to build 80 engine by = (6 × 80)/8 workers = 60 workers∴ extra workers = (60 - 40) = 20 workers