Let "n" be the (unknown) number of workers. Then the rate of work waslamps per worker per month BEFORE increasing. From the other side, the rate of work became lamps per worker per month AFTER increasing. From the condition, we know that the difference in the rate of work is 40 lamps per worker per month. It gives you an equation - = 40, or = 40, n = = 5. ANSWER. The number of workers is 5.