TEACHER EDITION

Multiplying by 10, 100, and 1,000

Grade 5 · Lesson 2 · Dimensions 5A p.8
Math Book 5 · sheet 2
Warm-up — yesterday: Numbers to One Billion
What is the value of the 8 in 380,000,000?
80,000,000

What we are learning

Multiplying by ten moves every digit one place to the LEFT. The zero that appears is a consequence, not the rule.

How it is done — keep this beside you

These steps stay on your page while you work. If you get stuck, find the step you are on and read it again before you put your hand up.

1
36 in a place-value chart.
| 3 | 6 |
2
Times ten: every digit shifts one place left.
| 3 | 6 | | 3 | 6 | _ |
3
The ones place is now empty, so a 0 holds it.
| 3 | 6 | | 3 | 6 | _ | 360
4
Times ten again — shift again.
| 3 | 6 | | 3 | 6 | _ | 360 3,600
5
So × 100 is two shifts. Not 'add two zeros' — SHIFT twice.
| 3 | 6 | | 3 | 6 | _ | 360 3,600 36 × 100 = 3,600

Practice

I DOteacher builds it, nothing erased
47 × 100
  1. Two shifts left.
  2. 4 and 7 move; two places open up.
  3. 4,700
WE DO 1together, on whiteboards
512 × 10
One shift. Say where each digit lands. Boards up.
  1. 5,120
WE DO 2together, on whiteboards
80 × 1,000
This one already ends in a zero. Shift anyway.
  1. Three shifts.
  2. 80,000
YOU DOindependent, from the book
Book 5A p.8 — the Do section, clipped onto the slide
the book page
Ask yourself: “How many places is everything moving?”
Watch for
'Add zeros' works here and fails the moment decimals arrive in this same chapter — 0.8 × 10 is not 0.80. Teach the shift now and the decimal lesson costs nothing later.