Solution: average time that 3 lawn mowers operate = 930 min. on given day total time they take for a day = average time per day x quantity of lawn mowers this gives, 930 x 3 = 2790 minimum time that a lawn mower can operate = 900 min hence, minimum two mowers can operate at 900 min then third mower will take time, that will be ,2790 = ((2 x 900) + third mower time) that will give , 990 min. Hence, one of the mowers can operate for about 990 min.