Math Meeting Lesson 2 8 Multiplicative Comparison Math

Math Meeting

Lesson 2 -8 Multiplicative Comparison

Math Message – pg 71

Share your statements The length of Maxine’s ribbon is 2 times the length of Eve’s ribbon. Maxine’s ribbon is twice as long as Eve’s Two of Eve’s ribbons would be equal to the length of Maxine’s ribbon Eve’s ribbon is half the length of Maxine’s because 8 is half of 16. These statements are called comparison statements.

They include information about both quantities, or amounts, being compared. Here are some comparison words and ideas: shorter than, longer than, two of this will equal that, two times as long as, and so on. Two quantities are in a relationship with each other – one quantity is a number of times as long as the other. The relationship involves multiplication, so these specific statements are called multiplicative comparison statements.

A DVD costs $15 and a book costs $5. Make a multiplicative comparison statement about the two objects. Examples: The DVD costs 3 times as much as the book. Three books equal the cost of one DVD. What equation can you write to describe the relationship between the DVD and the book?

A DVD costs $15 and a book costs $5. There is multiplicative thinking behind the comparison situation. What does the 5 represent? What does the 3 represent? What does the 15 represent? What is the mathematical relationship between the costs of the two items?

Looking back to the math message … What equation can you write to describe the relationship between the two lengths?

Solve the following problem. Scarlett has 7 crayons in her pencil box. Liam has 4 times as many crayons as Scarlett. How many crayons does Liam have What strategies did you use to solve the problem?

You have used multiplication to solve different types of problems: equal groups, arrays, and area models. Another type of multiplication problem focuses on comparing two quantities. It involves showing that one quantity is a specific number of times as many or as much as the other.

Scarlett has 7 crayons in her pencil box. Liam has 4 times as many crayons as Scarlett. How many crayons does Liam have? Whose number of crayons is greater? How do you know? How many times as great? Will Liam have more or fewer than 7 crayons? Explain your thinking.

Let’s write an equation What number is 4 times as many as 7? What equation can we write to represent this situation?

3 * 9 = 27 Will has 9 CDs. Jeremy has 3 times as many CDs as Will. How many CDs does Jeremy have? Does the equation represent the situation in the number story? How do you know? What How is the comparison being made in this number story? do you know that one quantity in this equation is a number of times as many as another quantity in this equation?

20 = 5 * 4 20 is 5 ties as much as what number? 20 is 4 times as much as what number? So we can say that 20 is 4 times as much as 5; or 20 is 5 times as much as 4. What comparison number story can you create to match this equation?

Work in pairs to complete journal page 53.

Summarize Share your comparison number stories from Problem 6 on journal page 53.

Exit Ticket Lyniah’s rope is 2 times as long as Peter’s rope. If Peter has 9 feet of rope, how many feet of rope does Lyniah have?