how do you solve SAT practice test #7 section 4 question 26?

Tricky one, right? To get it, you need to first recognize that the table on the previous page gives you food calories per gram of protein, fat, and carbohydrate. So you know that:

  • A gram of protein is 4 food calories
  • A gram of fat is 9 food calories
  • A gram of carbohydrate is 4 food calories

So now back to #26, which tells us that 180 food calories is the sum of the calories from p grams protein, f grams fat, and c grams carbohydrate. From the list above, we know, for example, that p grams protein will mean 4p food calories, and so on and so forth for fat and carbohydrates.

So we can write an equation:

4p + 9f + 4c = 180

Now all we need to do is manipulate, because the question asked for f in terms of p and c.


Watch that last step! When you factor -\dfrac{4}{9}, you need to be careful with your minus signs.

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