Correct answer:
From the first part of the condition, the rate of work of one worker per day is. Next step is to find how many men is required to plough 250 acres in 21 day. For it, divide by the rate of work of one worker per day: : = = = = = 5*5 = 25. Now the answer to the problem's question is: 25 - 15 = 10 more men will be required. Answer. 10 more men will be required.