Measuring with Fractions

Children practice working with fractions by using cups and tablespoons to measure ingredients. Children will compare and add fractions to measure the correct amount of each ingredient. Students use each kind of measuring tool to efficiently measure fractions of cups and tablespoons when baking. 

Introduction:

• Inform your students that they will be exploring how we can use math in the real world by thinking about food and baking. Challenge your students to think about how math shows up in baking. Here are some ideas:  
  • Fractions in cup and tablespoon measurements 
  • Weight and measurement of ingredients 
  • Operations, such as adding different ingredients into a bowl 
  • Creating arrays when laying out cookies on a baking sheet 
  • You can also ask students for some of their favourite things to bake, and then walk through the steps of the recipe to identify the different ways in which math is needed. 
• Lead a five-minute refresher lesson on the different parts of a fraction.

Lesson: 

•  Sort children in groups of 4-6.  
• Each group should have a set of materials including a tablecloth, measuring cups and spoons, a bowl, and dry ingredients like flour or salt. They will also need notebooks to write down equations. 
• Tell children to use the measuring cups first to measure out one cup. Remind them that baking is very precise, so they should only put exactly what they need in the bowl and should make sure that their measured cups are level and not overflowing. 
• Then tell children to use a different measuring cup (1/2, 1/3, or 1/4) to measure out the same whole cup of flour. Tell them to write out an equation for how much they have added to the bowl and challenge them to prove how they know how many 1/2 cups make up a whole cup. 
  • For example, you need 2 x 1/2 cup to make 1 whole cup, because 1/2 + 1/2 = 1. 1/4 + 1/4 + 1/4 + 1/4 = 1, etc. 
  • Students should take turns measuring the ingredients and writing an equation that represents how much they have added to their bowl.  
    • There will be many correct answers here: some students may add 1/2 + 1/2 to make 1 cup, while others may experiment with adding 1/2 + 1/4 + 1/4 to make 1 cup. The emphasis is on representing what you have added as an equation. 
• Ask children to share the different equations they found with the class that make 1 cup. 
  • How many 1/2 or 1/4 cups are the same as 1 cup?  
  • How do they know, and how could they show their thinking with an equation? 
• Ask children to repeat what they just did with tablespoons. How many 1/2 tablespoons does it take to make a whole tablespoon?
• Tell students they are going to use their fraction knowledge to measure ingredients. You are going to play a game and see who can create different measurements the fastest within their group.
  • In the first round, tell students to use the different measuring cups to figure out how to make 4.5 cups with the least number of pours. Certain measurements will be easier or harder for each kind of measuring tool they choose to use.  
    •  Ask children to predict as a whole class whether they think the whole cup or half cup will make the fastest and most accurate measurement.
    • Give the children some time to fill their bowls. Tell them to keep track of what measuring cups they are using to make an equation for 4.5 cups.  
      • E.g. 1 cup + 1 cup + 1 cup + 1 cup + ½ cup 
    • Give children some time to compare their bowls and equations between groups and talk about which cup was more useful and why. Ideally children will realize that the half cup is useful because it can make both 1 cup and a 1/2 cup, while the whole cup can only make 1 cup and needs an estimation to make a 1/2 cup. The whole cup makes 4 cups in 4 pours, while the 1/2 cup needs 8 pours to make 4 cups. 
  • In the second round, tell students to use the different measuring cups to figure out how to make 3 2/3 cups in the least amount of pours. This time, they cannot use the whole cup. They must use a combination of the 1/2, 1/3, and 1/4 cups for this task. 
    • Ask the children to predict as a whole class which other cups would be most useful for making a whole cup. Can all of them make a whole cup? 
    • Give the children some time to fill their bowls. Tell them to keep track of what measuring cups they are using to make an equation for 3 2/3 cups. 
      • E.g. 1/2 cup + 1/2 cup + 1/2 cup + 1/2 cup + 1/2 cup + ½ cup + 1/3 cup + 1/3 cup 
    • Give children some time to compare their bowls and equations between groups and talk about which cup was more useful and why. 
  • For the final round, challenge students to make 2 1/2 cups using exactly 7 pours. 
    • Ask children if they have any starting ideas to solve this problem. How can they use their fraction knowledge to know where to start? 
    • Give the children some time to fill their bowls. Tell them to keep track of what measuring cups they are using to make an equation for 2 1/2 cups in exactly 7 pours. Some solutions include… 
      • 1/2 cup + 1/2 cup + 1/4 cup + 1/4 cup + 1/4 cup + 1/4 cup + 1/2 cup = 2 1/2 cups 
      • 1/2 cup + 1/2 cup + 1/3 cup + 1/3 cup + 1/3 cup + 1/4 cup + 1/4 cup = 2 1/2 cups 
      • 1 cup + 1/4 cup + 1/4 cup + 1/4 cup + 1/4 cup + 1/4 cup + 1/4 cup = 2 ½ cups
    • Give children some time to compare their bowls and equations between groups and talk about which cup was more useful and why.

Conclusion: 

• Ask children what strategies they used to measure out a fraction that they did not have the right measurement tool for. 
• Ask children what further questions they have about fractions based on what they learned and saw today.
• Tell children that they have learned some of the building blocks of ingredient measurement using fractions and will soon be able to make a whole recipe with multiple ingredients in different fractions.