Hi,

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

i.e, 5: 15 = 28 : x

Or, x = (28*15) / 5

Or, x = 84 days

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

Hope this information is helpful

Thankyou.