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Help me solve this nutritional problem

Assume that your energy cost of foraging is 300 kcal/hour above your basal metabolic rate of 100 kcal/hour. (Assume also when you are NOT foraging, you are resting). On average, while foraging, you procure 1,500 kcal/hour. How many hours per day do you need to forage to break even? If, instead, you forage for twice this duration (and eat all that you procure), approximately how many grams of fat would you store each day?
8 hours; 100 grams
2 hours; 250 grams
4 hours; 250 grams

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Bruce P. | 20+ year college biology/genetics teacher; I love teaching one-to-one!20+ year college biology/genetics teache...
4.9 4.9 (158 lesson ratings) (158)
Susana: The problem breaks down into two pieces.
1) Calculate you expenditures. They come in two pieces--your UNAVOIDABLE (basal) rate of 100kcal/hour. So all hours spent NOT foraging incur 100/hour price... then there is your FORAGING rate--300/hour. There are 24 hours in a day, so your if you assign X as the number of hours foraging, your basal hours must be (24-x).
2) Your 'profits' or income: 1500/hour. Note that you can simplify your foraging value to be (profits-cost) or (1500-300) or NET increase 1200/hour
While you could write a generalized equation, it looks like you're only given 3 foraging times (2, 4, 8 hours) so you can just solve each.
For the FAT grams, you need to find a value your instructor or text has given you that tells you how many grams of fat are created per (100) calories. Then take your first answer (# hours for break even) and double the foraging value it gave you.