If 15 men can reap the crops of a field in 28 days, in how many days will 5 men reap it?

Question: If 15 men can reap the crops of a field in 28 days, in how many days will 5 men reap it?

Solution:
Let 5 men can reap a field in x days
So, put the same quantities on the same side.
Men: Days
Now, Men and Days are inversely proportional to each other. If we increase the number of men fewer days will be required to complete the work.
Inversely proportional means = 15 = 1/28, 5 = 1/x
so, 5/15 = 28/x
⇒ 5x = 28 × 15
∴ x = 84

Hence, 5 men can reap a field in 84 days.