Cogito
Grade 5 Math · Chapter 2 · Lesson 2
Dividing by Two Digits
Guess how many fit, then check.
10 problems · about 17 minutes · 5.NBT.B.6
What this lesson teaches
The child divides by a two-digit number by estimating how many groups fit and adjusting.
- Division asks how many groups fit.
- Take out easy chunks, then add the chunks up.
- A guess that is too small only costs a step.
Warm-Up Review
From earlier lessons. Loosen up before the new work.
2 problemsReview — Multiplying Large Numbers: 124 × 12 = ?
Answer 1488
Why 1,488.
Review — Rounding Decimals: Round 7.63 to the nearest whole number.
Answer 8
Why 8.
Warm Up
Straightforward practice. Get the method working first.
4 problems552 ÷ 24 = ?
Answer 23
Why 20 + 3 = 23.
What does 624 ÷ 24 ask?
Answer How many 24s fit into 624.
Why It asks how many groups of 24 fit.
360 ÷ 15 = ?
Answer 24
Why 20 lots is 300.
468 ÷ 12 = ?
Answer 39
Why 30 lots is 360.
Build It Up
The same ideas with more to keep track of.
2 problems798 ÷ 21 = ?
Answer 38
Why 30 lots is 630.
Is it a problem if your first guess is too small?
Answer No. It just takes another step.
Why You can always take out more.
Stretch Yourself
Mixed problems. Work out what kind of question it is before you start.
2 problemsThe Coach Trip: 432 children in coaches holding 36. How many coaches?
Answer 12 coaches
Why 10 + 2 = 12 coaches.
The Packing: 575 books packed 25 to a box. How many boxes?
Answer 23 boxes
Why 20 + 3 = 23 boxes.