Question

12 men or 18 women can reap a field in 7 days, in what time can 4 men and 8 women reap the same field?

Answer 1

Since 12 men can reap the field in 7 days . One man can reap (1/12*7) = (1/84)th field a day.

Since 18 women can reap the field in 7 days . One women can reap (1/18*7) = (1/126)th field a day .

Now we have 4 men and 8 women working . So, the total number of days taken would be the reciprocal of:

4*(1/84)+8*(1/126) = 7/63 = 1/9

Therefore 4 men and 8 women reap the same field in 9 days