Fractions and Feeding a Group of People
Feeding a group of people can be difficult, especially when it comes to Multiplying Fractions by a Whole Number in the recipe. So often we hear kids ask, ”When am I ever going to use this?” Well, if they are ever going to follow a recipe, the answer to that is potentially every day! I am not a good cook. But occasionally I find a recipe that my family loves, and I almost always have to make 1 ½ -2 times the amount to feed them. Voila! Using fractions every day. I often find myself stopping to really think about fractional amounts in recipes when I need to change the amount I am making. Especially when it comes to the spices. If I don’t deal with my fractions correctly, it alters the taste of the whole meal.
A great way to get your students working with fractions is to let them make their own snack in school! Here’s a fun way to multiply fractions by whole numbers while making tasty, strawberry smoothies.
Set Up for the Lesson: Multiplying Fractions by a Whole Number Hershey Chocolate Smoothies
- Each student needs their math notebook or a piece of paper
- 6 pack of Hershey Chocolate bars
- Large pitcher for a blender – or if your school cafeteria has a large one you can use, even better
- Milkshake ingredients
- Various sizes of measuring cups and measuring spoons – if you do not have standard measuring cups, you can mark clear plastic cups with a permanent marker to the appropriate amounts – ½, ⅓, ¼
- One cup for each student to have a milkshake
- Plastic gloves – one pair for each student who is adding ingredients
Launch the Lesson: Multiplying Fractions by a Whole Number
Show the class you have a 6-pack of Hershey Chocolate bars. Take one of the bars and tell the class that you are thinking of giving each student half of a chocolate bar. Break it in half so they have a visual. You may need a pair of cooking shears to cut through the wrapper. Hold up your two halves. Next, ask them if you have enough to give every student in the class half of a chocolate bar. Wait here and let them do the math. Give them a little more time than you think to let the answer sink in. Some of them will sigh and groan. Others will yell out, “That’s not fair! There’s not enough!”
Ask them to write out in their math notebook how they determined if you had enough bars to give each student half a chocolate bar. They can draw pictures or write equations – whatever works for them. Ask them to turn to a friend and explain their answer. Do they agree? How many students will get a half of a chocolate bar? Ask students to share what they wrote on their papers. Put their explanations on the board. Try to choose students who did this in different ways so that you can see as many strategies as possible. In the end, students should come up with something like ½ bars * 30 students = you need 15 bars (substitute your number of students). No, there are not enough bars in the pack for everyone to get ½.
On the board write ½ * 30 = 15. Ask the students to explain how they arrived at that answer. What is the step by step procedure? Review the algorithm. ½ * 30/1 = 30/2 = 15. Do a few more practice problems to be sure they are ready for the next step. Try these problems:
- ⅓ * 3 = 3/3 = 1
- ⅛ * 4 = 4/8 = 2
- 1/12 *9 = 9/12 = 3/4
Consider handing out squares of chocolate from the Hershey bars as a reward to students who are actively working through these problems…try to find a reason to give one to every student in the class.
The Lesson: Multiplying Fractions by a Whole Number
Now we get to the fun part! Divide students into groups of 4, 5, or 6 (so you have 5 groups total). Give one recipe worksheet to each person. I like to have each student use their own worksheet – that way everyone does the work. Students can come together at the end to check each other’s work, and they can help each other if they get stuck.
Introduce the Lesson
Introduce the activity to the class. We are going to celebrate how much we love math today. When we go to a party, we always get some food. How does the host of a party decide how much food they need? Wait for students to pair and share their answer. That’s right. They need to know how many people there will be, and then they multiply the serving size for each food item by that many people to get a rough estimate. You don’t want your guests to go hungry!
Making Milkshakes
Today, we are going to make milkshakes to help us celebrate. Handout the Milkshake Math worksheet with the recipe. As you can see, each batch makes four milkshakes. One batch includes:
- ¾ cup strawberries (fresh or frozen)
- ½ cup cashews (must be unsalted, can be roasted or raw)
- ¾ teaspoon sugar
- 1 ¼ teaspoon vanilla extract
- 2 ½ cups milk or non-dairy alternative
Teaching Tip
I recommend laying down some pretty strict ground rules so that the lesson will be a success, especially when there is food involved. I find that if the kids know they get to have a treat in the end, they will be on board. Here are the rules I use in my class:
- Eat only when instructed to.
- Food that touches the desk or the ground goes directly into the garbage.
- Do not share or switch food with other students.
- Follow directions so that food is not contaminated.
- Wear your gloves at all times.
Safety Rules
There are also some safety rules to keep in mind when using food. Be sure you know each students’ health status and are aware of any allergies. Stay clear of those foods that are a risk. There are plenty of foods that are safe for kids who have allergies. I used this recipe. The cashews can be eliminated if students are allergic.
Multiplying Fractions by a Whole Number Milkshake Math Worksheet
Each group will use the recipe on the Milkshake Math Worksheet to answer the questions and find out how much of each ingredient is needed to make a milkshake for everyone in the class. Before you make the milkshake, each student must do the math. Let them work through problems in a group to reduce the pressure of getting all correct answers on their own. Refer them to your examples on the board if they need help. Circulate around the room asking questions and helping groups that are stuck.
Download and Print These Worksheets:
Milkshake Math Worksheet (PDF)
Milkshake Math Worksheet (Doc)
Have one student from each group go to the board and show their math work for how they figured out the total amount for one of the ingredients.
Have the students choose one person from their group to get a pair of gloves and come forward to add that ingredient, using their worksheet to inform how much they need. Oversee these students to be sure they are adding the correct amount. If your blender is not big enough to make enough for the whole class, you may need to do half the class at a time – a whole other level of using fractions!
Reflecting on the Activity: Multiplying Fractions by a Whole Number
How fun was this lesson?! As they are all enjoying their milkshakes, you can talk about food that they have had at parties. How much is there? Has the host of a party you’ve been to ever run out of food? Why did that happen? How can you tell how many servings are in a package of something? How can you avoid this problem at a party?
On a smaller scale, have them think about how many people are in their families. If they were following a recipe for their family would they have to double it? Halve it? What happens if you run out of food at a meal?
Extensions/Next Steps
This is a great chance to talk about food labels. You can look at how many servings there are in a package. And how much of each ingredient there might be. For example, ¼ teaspoon of sugar is one gram. You can see how many grams of sugar there in foods. Add this amount of sugar to a baggie, and kids are amazed at how much sugar they eat!
Extra Resources
https://mykidslickthebowl.com/healthy-strawberry-milkshake/
FREE Multiplying Fractions by a Whole Number Worksheets PDF and Resources
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- 5-2 Assignment SE – Multiplying Fractions and Whole Number (PDF)
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5-1 Fractions as Division
5-2 Multiplying Fractions and Whole Number
5-3 Multiplying Fractions
5-4 Interpreting Multiplication
5-5 Multiplying Mixed Fractions
5-6 Dividing Unit Fractions by Whole Numbers
5-7 Dividing Whole Numbers by Unit Fractions
5-8 Fractions in Real World (Multiplication and Division)