Ray's New Practical Arithmetic · Arts. 27–30 · Unit 4: Multiplication
14. What multiplication is
Goal: Your child explains multiplication as adding equal numbers, names its parts, and knows the order of factors does not matter.
You'll need
- The book
- A slate, small whiteboard or scrap paper
- A notebook and pencil
What's in the book
Short problems solved by adding equal numbers, the definitions of multiplication, multiplicand, multiplier, product and factors, the sign ×, the multiplication table, and the principle that order does not matter. (Printed pages 39 to 42 are missing from this scan, so the page shown is p. 43; the quotes below are from another copy of the same edition.)
The lesson, step by step
Warm-up
Do the book's first problems aloud:
If 1 orange cost 2 cents, what will 3 oranges cost?
If 1 lemon cost 3 cents, how many cents will 4 lemons cost?
Answer by adding: 2 + 2 + 2 = 6; 3 + 3 + 3 + 3 = 12.
The idea
Read:
Multiplication is taking one number as many times as there are units in another.
Say4 rows of 21 trees is 21 + 21 + 21 + 21. Multiplying is a short way to do that adding.
The words
Read:
The multiplicand and multiplier are together called factors, because they make or produce the product.
Write 21 × 4 = 84 and label the multiplicand, multiplier and product.
Order does not matter
Read:
The product of two numbers is not altered by changing the order of the factors.
Show with beans: 3 rows of 5 and 5 rows of 3 are both 15.
The table
Read through the multiplication table in the book. Your child recites any rows that are not yet solid (often 7s, 8s, 12s).
Wrap-up
Quick-fire: 6 × 7, 8 × 9, 12 × 11, 7 × 8, 9 × 6.
Afterwards
Drill the table rows that are slow, a few minutes a day.