If 5 men working 6 hours a day can reap a field in 20 days, in how many days will 15 men reap the field if they work for 8 hours a day?
Instead of working with a number of men and the number of hours in a day, consider the number of 'man-hours' used.
The entire task of reaping the field takes:
The question involves inverse proportion because if there are more men working and they work for more hours each day, then the task will be completed in fewer days.
To complete the task which requires