Explain the use of placeholders when multiplying whole numbers by 100 | Maths

Starter quiz

What number is being represented using the Base 10 blocks?
- '131' ✓
What number is being represented in the place value chart?
- '234' ✓
What number is being represented using the place value counters?
- '222' ✓
What number is being represented using the Base 10 blocks?
- '700' ✓
What number is being represented in the place value chart?
- '6,632' ✓
What number is being represented using the place value counters?
- '2,222' ✓

Exit quiz

Look at the image. The label below the arrow is missing a number. Complete it. ______ times the size.
- '100' ✓
Which of the following equations is represented by the place value counters and the arrow in the image?
- 4 × 100 = 400 ✓
- 100 + 100 + 100 + 100 = 400
- 400 ÷ 100 = 4
True or false? To multiply a whole number by 100, you just add two zeros.
- True
- False ✓
Which of the following equations is represented by the place value counters and the arrow in the image?
- 12 × 100 = 1,200 ✓
- 12 + 1,000 = 1,012
- 1,200 ÷ 100 = 12
What is the equation being represented in the place value chart showing before and after?
- 320 × 1 = 320
- 32 × 100 = 3,200 ✓
- 5 + 5 = 10
- 3,200 ÷ 10 = 320
Match the numbers with the numbers that are 100 times the size.
- 6
  
  ⇔
  
  600 ✓
- 13
  
  ⇔
  
  1,300 ✓
- 27
  
  ⇔
  
  2,700 ✓
- 99
  
  ⇔
  
  9,900 ✓

Worksheet

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Presentation

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Lesson Details

Key learning points

Multiples of 100 have zero in the tens and ones column.
When a number is multiplied by one hundred the product is a multiple of one hundred.
Multiplying by one hundred moves all the digits two columns to the left making the digits one hundred times the size.

Common misconception

Many pupils believe that 'adding 2 zeros' is multiplying by 100 which can lead to difficulties later on when they are introduced to decimal numbers.

Don't dismiss it. It's a pattern that has been spotted and generalised. Do encourage the children to work with physical resources that don't involve the numbers themselves so they can understand that it isn't adding zero but changing place value.

Keywords

Placeholder - A placeholder is where we use the digit 0 to hold a place in a number and maintain place value.
Magnitude - The magnitude of a number is its distance from 0