Minds On
Doubling a recipe
A student is going to make a cupcake recipe, but they decide they want to double the recipe to make extra cupcakes to bring to a community gathering. To double the recipes means to add everything twice.
They start with the first ingredient which is cup of flour.
Brainstorm
Brainstorm
How do we add ?
Record your thinking using pictures, tools such as fraction strips or circles, or using an audio recording. If possible, share your thinking with a friend.
Action
Adding fractions
You need to have a common denominator when adding or subtracting fractions so that you are working with the same size pieces of a whole.
Check out this video from TVO Homework Zone entitled “All About the Denominator” to learn more about the importance of the denominator.
Let’s consider the following scenario about feeding an adult cat and a kitten.
Feeding a pet
An adult cat and a kitten are each served a quarter of a can of cat food in the morning and a quarter of a can of cat food at dinner time.
The adult cat is especially hungry in the morning. It eats its own portion of food as well as the kitten’s morning portion.
We can express the total amount of food the adult cat ate by adding the fractions:
The following image shows the sum of these fractions expressed in fractional notation.
Three circles, each divided into four pieces. One of the four pieces from each circle is shaded. One fourth of a whole circle, plus one fourth of a whole circle, plus one fourth of a whole circle. In fraction form, the expression reads one fourth, plus one fourth, plus one fourth.
The sum of one-fourth plus one-fourth plus one-fourth equals three-fourths.
The fractions that were added in the question have the same denominator. This means the whole is divided into the same total number of equal parts. This also means the pieces, or fraction amounts, are the same.
Subtracting fractions
Let’s consider the same scenario but from another way.
The kitten is supposed to eat two fourths of food but one fourth is eaten by the adult cat.
We can express this as a subtraction statement:
Two fourths minus one fourth equals one fourth.
Your turn!
Let’s practice adding and subtracting fractions.
In your notebook or using another method of your choice, complete the following questions.
| Adding fractions | Subtracting fractions |
|---|---|
|
|
|
Alternately, you may choose to complete the Fraction Statement Practice Sheet in your notebook or using the following fillable and printable document. If you would like, you can use speech-to-text or audio recording tools to record your thoughts.
Press the Activity button to access Fraction Statement Practice Sheet.
Activity (Open PDF in a new tab)Consolidation
Research and discuss
Consider what is necessary to be able to add or subtract fractions.
What do we need to notice before we can proceed?
Your task
Choose from the following options:
- Create a presentation through writing, sharing out loud, an audio recording, or a method of your choice, that explains to other students how to add and subtract fractions.
- Create some practice fraction addition and subtraction questions that other students could solve.
- Create a word problem that requires either the addition or subtraction of fractions with like or same denominators.
Pause and Reflect
Pause and reflect
What are some real-life situations where we may need to add and/or subtract fractions?
Record your thinking in print, digitally, or using an audio recording. If possible, share with a partner.
Reflection
As you read through these descriptions, which sentence best describes how you are feeling about your understanding of this learning activity? Press the button that is beside this sentence.
I feel...
Now, record your ideas using a voice recorder, speech-to-text, or writing tool.