Cogito
Grade 3 Math · Chapter 1 · Lesson 6
Multiplying by 2, 5, and 10
The three easiest tables, and why they are easy.
10 problems · about 12 minutes · 3.OA.C.7
What this lesson teaches
The child recalls the 2, 5, and 10 times tables and explains the pattern in each.
- The 2 times table is doubling.
- The 10 times table always ends in 0.
- A five is half of a ten, so halve the ten answer.
Warm-Up Review
From earlier lessons. Loosen up before the new work.
2 problemsReview — Multiplication and Division Fact Families: You know 6 × 4 = 24. What is 24 ÷ 6?
Answer 4
Why 24 ÷ 6 = 4.
Review — Division as an Unknown Factor: 45 ÷ 5 = ?
Answer 9
Why 9 × 5 = 45.
Warm Up
Straightforward practice. Get the method working first.
4 problems7 × 5 = ?
Answer 35
Why 7 × 5 = 35.
What do all the answers in the 10 times table end in?
Answer 0
Why Every multiple of ten ends in 0.
7 × 2 = ?
Answer 14
Why Double 7.
6 × 5 = ?
Answer 30
Why Half of 60.
Build It Up
The same ideas with more to keep track of.
2 problems8 × 10 = ?
Answer 80
Why 8 tens.
9 × 5 = ?
Answer 45
Why Half of 90.
Stretch Yourself
Mixed problems. Work out what kind of question it is before you start.
2 problemsThe Coins: Ana has 7 five-pence coins. How many pence is that?
Answer 35 pence
Why 7 × 5 = 35.
The Boxes: 9 boxes each hold 10 pencils. How many pencils?
Answer 90 pencils
Why 9 × 10 = 90.