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The purpose of this Number Talk is for students to demonstrate the strategies and understandings they have for multiplying whole numbers by fractions. These understandings help students develop fluency and will be helpful later in this lesson when students will need to be able to solve problems involving multiplication of a whole number by a fraction.
Find the value of each expression mentally.
Info Gap Picking Fruit Cards
This activity, which features an Information Gap routine (also Info Gap routine), gives students an opportunity to solve problems about data represented on line plots. In both sets of cards, there is a partially complete line plot and some unknown data.
This activity uses MLR4 Information Gap.
For the first set of cards, the Problem Card has the unknown data and the Data Card has a partially complete line plot. Monitor for students who request:
For the second set of cards, the Problem Card has the partially complete line plot and the Data Card has information to determine the unknown data. Here students likely will need to communicate with each other as the information about the most common weight is vital to solve the problem, but the student with the Problem Card may not think to ask about this.
The Info Gap routine allows students to refine the language they use to ask increasingly more precise questions until they get the information they need (MP6).
MLR4 Information Gap
Your teacher will give you either a Problem Card or a Data Card. Do not show or read your card to your partner.
Pause here so your teacher can review your work. Ask your teacher for a new set of cards and repeat the activity, trading roles with your partner.
Optional
The purpose of this optional activity is for students to answer questions about a line plot, using the same context as in the previous activity. Students relate repeated addition of the same fraction to multiplication which they studied in a previous unit. They also address a question about the sum of all of the data. Because there is a lot of data, there are many viable strategies to answer this question and the Activity Synthesis focuses on sharing these strategies.
When students solve problems about the apricot weights, using the line plot, they reason abstractly and quantitatively (MP2).
This line plot shows the weights of the apricots that Mai picked.
“We have added, subtracted, and multiplied fractions to solve problems about line plots.”
“In what ways did we use these operations to help us solve problems about line plots?” (Line plots have a lot of different data and the data had fractions, so when we answered questions about the data, we had to add, subtract, or multiply.)
“Which was your favorite problem about line plots?” (The eggs because I thought the picture was really interesting.)
We learned to add and subtract fractions.
We learned how to add and subtract fractions with denominators that are the same.
Example:
We add the tenths. There are 11 tenths, so .
We also learned how to add and subtract fractions with denominators that are not the same.
Example:
We look for a common denominator, so we can add parts of the same size.
One way to find a common denominator is to use the product of the two denominators. This is always a common multiple.
Using 48 as a denominator, we find . This means .
We also can use a smaller common denominator.
Since 24 is a multiple of 6 and 8, we can rewrite as , which is .