Cogito
Grade 3 Math · Chapter 3 · Lesson 7
Missing Factors and Divisors
Finding the gap in any position.
10 problems · about 13 minutes · 3.OA.A.4
What this lesson teaches
The child finds an unknown factor, divisor, or dividend in a multiplication or division equation.
- The gap can be in any position.
- The other two numbers name the fact family.
- Check by putting your answer back in.
Warm-Up Review
From earlier lessons. Loosen up before the new work.
2 problemsReview — Multiplying by Multiples of Ten: 7 × 40 = ?
Answer 280
Why 7 × 4 = 28, so 7 × 40 = 280.
Review — The Associative Property: 2 × 5 × 6 = ?
Answer 60
Why Grouping the 2 and 5 first makes it 10 × 6.
Warm Up
Straightforward practice. Get the method working first.
4 problems7 × ? = 63
Answer 9
Why 7 × 9 = 63.
? ÷ 5 = 7. What is the missing number?
Answer 35
Why 35 ÷ 5 = 7.
8 × ? = 56
Answer 7
Why What times 8 makes 56?
? ÷ 6 = 8
Answer 48
Why 6 shares of 8.
Build It Up
The same ideas with more to keep track of.
2 problems45 ÷ ? = 5
Answer 9
Why 5 times what makes 45?
? × 9 = 72
Answer 8
Why What times 9 makes 72?
Stretch Yourself
Mixed problems. Work out what kind of question it is before you start.
2 problemsThe Missing Factor: 6 × ? = 42. What is the missing factor?
Answer 7
Why 6 × 7 = 42.
The Missing Divisor: 36 ÷ ? = 9. What is the missing number?
Answer 4
Why 36 ÷ 4 = 9.