The American Heart Association (AHA) recommends that you get less than 30% of your daily calories from fat. You can use what you know about proportions to figure out the percentage of calories from fat in any food.
Let’s look at one example: a milkshake. Imagine a milkshake has 400 total calories, and 100 of those calories are from fat. You know it is tasty, but is it healthy? You can find out by calculating the percentage of calories from fat.
A percentage is a mathematical way of comparing numbers to 100. So one way to think about 10%, for example, is "10 out of 100." To find the percentage of calories from fat to total calories, you can set up a proportion like this:
We used division here because the denominator 400 is 4 times bigger than the denominator 100. For this proportion to be correct, the numerator 100 also has to be 4 times as large as the number represented by ?. You can find that number if you divide 100 by 4. Thus, the shake has 25% calories from fat.
Now it is your turn. A sandwich has 200 calories, and 30 of those calories are from fat. In two to four sentences, describe how you could set up a proportion to figure out the percentage of calories from fat in this sandwich.