Fractions and Recipes (Investigation)

Objectives

• To practice with fractions in real life situations.
• To practice with the multiplication of fractions.
• To practice with fractions of a quantity.
• To practice with fractions as repeating decimals.

Materials

• Computer
• Calculator
• Crayons or markers
• 2 Pieces of construction paper
• Stapler

Procedure

Work on your own or in small groups to do the following.

1. Take the two pieces of construction paper and lay them on top of each other as shown.

2. Fold the pieces of paper so that the flaps are roughly the same size and staple the top to secure it. Your booklet should have 4 flaps.

3. Look up the recipe for your favourite brownies, cookies, or cake. The only requirement for the recipe is that the list of ingredients must have at least 4 fractions in it.

4. On the first flap of the booklet you created label it original recipe and indicate the amount of servings it will create. Then write down the ingredients necessary. 

 

5. On the second flap mark it as \frac{5}{6} of the original recipe. Next to this, indicate the servings this new recipe will produce. Above this label write the amount of each ingredient that will be required to make \frac{5}{6} of the original recipe.

6. On the third flap mark it as \frac{4}{5} times the original recipe. Next to this, indicate the servings this new recipe will produce. Above this label write the amount of each ingredient that will be required to make \frac{4}{5} times the original recipe.

7. On the fourth flap mark it as 15 times the original recipe. Next to this, indicate the servings this new recipe will produce. Above this label write the amount of each ingredient that will be required to make 15 times the original recipe. 

8. Add any design the booklet that you would like using your crayons or markers. 

 

 

Questions

1. Look at the ingredients in the second flap marked “\frac{5}{6} the original recipe.” Is there any other way to write these fractions? If so, rewrite them.
2. Look at the ingredients in the third flap marked "\frac{4}{5} times the original recipe.”  Convert the fractions in the list of ingredients into decimals using your calculator. Are any of these decimals repeating decimals? Why or why not?
3. Look at the ingredients in the third flap marked “15 times the original recipe.” Find the reciprocal for the amount of each ingredient. How did you do this? Explain.
4. How much of each ingredient would you need if you multiplied the amount of each ingredient from the original recipe by \frac{-1}{5}? Does this make sense for baking? Why or why not?
5. Would the answer change if you multiplied the amount required of each ingredient in the original recipe by \frac{-1}{5}? Explain.

Work with a friend for the following questions:

1. Is precision important in baking? Why or why not? How does knowing how to multiply and divide fractions help you with this?
2. Find the ingredients in your recipe that are also needed in your friend’s recipe. Who needs more? Why do you think this is?
3. How much of each ingredient do you think you would need to make enough to serve 100 people your chosen dessert? How much of each ingredient will your friend need to serve 100 people their dessert? 

 

 

Optional

Test it out! Pick one of the flaps in the booklet you’ve just created and try baking your chosen recipe according to the amount of each ingredient you calculated. Did it produce as many servings as you predicted?