Remaining food = Initial food provision - Food consumed in 15 days Remaining days of food = Remaining food ∕ Remaining men Calculation: Initial food provision =150 men ×85 days =12750 man-days 25 men left after 15 days Food consumed in 15 days =150 men ×15 days =2250 man-days Remaining men =150−25=125 men Remaining food = 12750 man-days - 2250 man-days = 10500 man-days Remaining days of food = 10500 man-days / 125 men ⇒ Remaining days of food =84 days