Cogito
Grade 2 Math · Chapter 5 · Lesson 4
Subtracting Within 1,000
Take away each kind of block in turn.
10 problems · about 12 minutes · 2.NBT.B.7
What this lesson teaches
The child subtracts three-digit numbers within 1,000 where no unbundling is needed.
- Subtracting three digits uses one more column.
- Check every column before you start.
- Take each kind of block from its own kind.
Warm-Up Review
From earlier lessons. Loosen up before the new work.
3 problemsReview — Making a New Hundred: 275 + 168 = ?
Answer 443
Why 275 + 168 = 443.
Review — Adding Within 1,000: 341 + 236 = ?
Answer 577
Why 341 + 236 = 577.
Review — Adding and Subtracting Hundreds: 400 + 500 = ?
Answer 900
Why 400 + 500 = 900.
Warm Up
Straightforward practice. Get the method working first.
3 problems758 − 326 = ?
Answer 432
Why 758 − 326 = 432.
How many columns do you check before starting?
Answer 3
Why All three, because any of them might be short.
578 − 234 = ?
Answer 344
Why Every column has enough.
Build It Up
The same ideas with more to keep track of.
1 problem869 − 415 = ?
Answer 454
Why 4 hundreds left.
Stretch Yourself
Mixed problems. Work out what kind of question it is before you start.
3 problems396 − 173 = ?
Answer 223
Why 2 hundreds, 2 tens, 3 ones.
The Warehouse: A warehouse had 795 boxes and sent out 342. How many are left?
Answer 453 boxes
Why 795 − 342 = 453.
The Journey: A trip is 680 km. 250 km are done. How far is left?
Answer 430 km
Why 680 − 250 = 430.