# Multiplying by ten

Purpose

The purpose of this activity is to support students to use multiplication by ten to find an amount ten times bigger than a given amount.

Achievement Objectives
NA2-4: Know how many ones, tens, and hundreds are in whole numbers to at least 1000.
Required Resource Materials
• Place value materials (e.g., BeaNZ, Iceblock sticks, place value blocks)
• Place value board (page 2)
• Calculator
Activity
1. Pose problems that involve ‘ten times more’, such as:
Here are seven unit cubes. If I make each cube ten times what it is, what number will I have?
2. Model the situation with place value materials by putting seven unit cubes in the ones place of the place value chart. Exchange each unit cube for a long (ten) and move the longs into the ten’s column.  What number is ten times seven?
What equation can we write for this problem?
Key in 10 x 7 = 70 on the calculator and record the equation.
3. Let the students solve similar problems with materials and record the operation using equations. After three examples they should anticipate the answer.
Examples might be:
What number is ten times six?
What number is ten times nine?
Discuss the meaning of the -ty numbers as groups of ten, e.g. sixty as six tens.
You might record 6 x 10 = 60 (six groups of ten) and 10 x 6 = 60 (ten times six) to help students see the connection to the commutative property.

Next steps

Increasing the level of abstraction by covering the materials, asking anticipatory questions, and working with more complex facts. Progress to working with the word problems or equations alone, e.g., What number is ten times eight?

Provide contexts in which multiplication by ten might be used, for example:

• Here are eight \$10 notes. How much money is that?
• Each packet has ten biscuits. There are seven packets. How many biscuits is that?