When deciding whether a food is healthy, it is important to look at the serving size and the servings per container—especially if you plan on eating the whole thing!
As the teens discover, juice containers often hold more than one serving of juice. But the teens can still make healthy decisions about what they drink by using proportional reasoning. Proportional reasoning can help you find out how much total sugar there is in a bottle of juice, a bag of chips, or your favorite candy bar.
A proportion is made up of two equal ratios. If you know how much sugar is in one serving, then you can set up a proportion to find the total number of grams of sugar in the entire bottle.
You know three of the numbers in this proportion.
For the proportion to be correct, the two ratios have to be equal. Look at the denominator (the bottom number in each ratio). The number 2 is two times as large as 1, so the number represented by ?, the numerator, must be two times as large as 18. The number 36 completes the proportion since 2 x 18 = 36.
The total number of grams of sugar in the drink is 36.