5-5 Multiplication Strategies: Doubling, Part 1

5-5 Multiplication Strategies: Doubling, Part 1

Math Message

Use your grid paper or white board.

One class sets up 4 rows of 6 chairs for a total of 24 chairs. Another class sets up 4 more rows with 6 chairs in each row. Now there are 8 rows of chairs with 6 chairs in each row. How many chairs are there all together?

Fill in the Blank

How many chairs did you find in the math message?

Solve using your white board or grid paper

Practice the doubling multiplication strategy

solve

Mrs Jones is making a room-number sign for her class that is 2 inches wide and 7 inches long. On your paper or white board, sketch the sign and the side lengths.

Now try this:

The librarian likes Mrs. Jones' room-number sign. She wants to make a larger sign that is 8 inches wide and 7 inches long for the library. How can the librarian use the area of the 4-by-7 sign to find the area of the new sign?

Multiple Choice

Which side length changes when we go from 4-by-7 sign to an 8-by-7 sign?

• 4 inches changes to 8 inches

• 4 inches changes to 7 inches

Fill in the Blank

What is the area of the librarian's 7-by-8 sign?

Practice your strategy on Math Journal Pages 164 and 165