Ray's New Practical Arithmetic · Arts. 9–10 · Unit 1: Numeration
3. Place value and periods
Goal: Your child explains why a figure's value depends on its place, tells odd from even, and groups the orders into periods of three.
You'll need
- The book
- A slate, small whiteboard or scrap paper
- A notebook and pencil
What's in the book
Article 9 lists nine definitions and principles about figures and their values. Article 10 groups the orders into periods: units, thousands, millions, and so on.
The lesson, step by step
Warm-up
Ask: Is 47 odd or even? 50? 83? Then: What is ten times 6? Ten times 60?
Even and odd
Read these two lines of Article 9.
The numbers that end with 2, 4, 6, 8, or 0 are called even numbers.
The numbers that end with 1, 3, 5, 7, or 9 are called odd numbers.
Local value
Read:
The value of a figure is always local; that is, it depends upon the place it occupies in a number.
The value of a figure is increased tenfold by removing it one place to the left.
Write 5, then 50, then 500. Say: Each move to the left makes the 5 worth ten times as much.
Periods of three
Read Article 10.
For convenience in writing and reading numbers, the different orders are grouped into periods of three orders each.
Write 4 250 873 with small gaps. Name the periods from the right: units, thousands, millions.
Try it together
Write 7 numbers of four to nine figures. Your child marks the periods with commas, counting three figures at a time from the right.
Wrap-up
SayWhich is worth more, the 3 in 300 or the 3 in 3000? How many times more? (Ten.)
Tip
Commas in big numbers are just period markers.