A charity kitchen has grain to serve 200 people for 40 days. If 50 people leave after 10 days, how long from now would the grain last?
Correct answer: B
Explanation
Total stock equals 200 x 40 = 8000 person-days. In the first 10 days, 200 people consume 200 x 10 = 2000 person-days, leaving 6000 person-days. With 50 people gone, 150 remain, so the grain lasts 6000 / 150 = 40 more days from that point.