A garrison of 1500 man has provisions for 6 weeks. At the end of the first two weeks 450 men desert. how long?

Okay so pretend each guy eats 1 pound per day of food. 1500 men times 42 days equals 63,000 lbs of total food. For the first two weeks, 1500 men eat 1 pound per day for 14 days, which adds up to 21,000 pounds. This leaves 42,000 pounds remaining. Since 450 men deserted, only 1050 men remain, and therefore the remaining food will be depleted at a rate of 1050 pounds per day. 42,000 pounds divided by 1,050 pounds per day equals 40 days.