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Study Guides > Prealgebra

Why It Matters: Fractions

Why demonstrate an understanding of fractions and how they relate to one another?

Chocolate chip cookies on a cooling rack Chances are your favorite recipe contains fractions.
Noelle is gathering ingredients to do her annual holiday baking. She's planning to bake chocolate cakes and cookies as gifts for her relatives. Noelle has 13 1/2 cups of flour, and she wants to bake as many chocolate cakes with it as she can. Then she plans to use any leftover flour to make cookies. Here's Noelle's recipe for chocolate layer cake:
  • 2 1/4 cups sugar
  • 2 cups flour
  • 3/4 cup unsweetened cocoa powder
  • 1 1/2 teaspoons baking powder
  • 1 1/2 teaspoons baking soda
  • 1 teaspoon salt
  • 2 eggs
  • 1 1/4 cups milk
  • 1/2 cup vegetable oil
  • 2 teaspoons vanilla extract
  • 1 cup boiling water
If she makes as many cakes as she can with her flour, how much flour will she have left to make cookies? How much of each ingredient will she need to make all her chocolate cakes? She also knows that her chocolate chip cookie recipe makes six cookies per 1/2 cup of flour. How many cookies will she be able to make with her leftover flour? To answer these questions, we need to know how to perform some basic operations with fractions. If you've ever tried to double a recipe or cut it in half, you've probably run into a few fraction problems in the kitchen, too. Let's explore how to work with fractions so we can help Noelle get her cakes and cookies in the oven.

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  • Chocolate chip cookies. Authored by: Kimberly Vardeman. Located at: https://commons.wikimedia.org/wiki/File:Chocolate_Chip_Cookies_-_kimberlykv.jpg. License: CC BY: Attribution.

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