Cogito
Grade 4 Math · Chapter 1 · Lesson 5
Adding Multi-Digit Numbers
The standard algorithm, and why it works.
10 problems · about 14 minutes · 4.NBT.B.4
What this lesson teaches
The child adds multi-digit whole numbers fluently using the standard algorithm.
- Line up like units in columns.
- Ten of any unit becomes one of the next unit up.
- Estimate first so a wrong answer stands out.
Warm-Up Review
From earlier lessons. Loosen up before the new work.
3 problemsReview — Rounding to Any Place: Round 6,349 to the nearest hundred.
Answer 6300
Why 6,349 is just before halfway.
Review — Comparing Large Numbers: Which is bigger, 32,450 or 32,405?
Answer 32450
Why 5 tens beats 0 tens.
Review — Reading and Writing Large Numbers: 60,000 + 700 + 8 in digits?
Answer 60708
Why 60,708.
Warm Up
Straightforward practice. Get the method working first.
3 problems3,758 + 2,496 = ?
Answer 6254
Why 3,758 + 2,496 = 6,254.
When a column of tens fills, what do you make?
Answer One hundred.
Why Ten of any unit make one of the next unit up.
2,486 + 1,375 = ?
Answer 3861
Why 6 and 5 makes 11.
Build It Up
The same ideas with more to keep track of.
1 problem5,092 + 3,918 = ?
Answer 9010
Why 2 and 8 makes exactly 10.
Stretch Yourself
Mixed problems. Work out what kind of question it is before you start.
3 problems4,679 + 2,845 = ?
Answer 7524
Why Regroup at three places.
Two Crowds: 3,486 people came on Saturday and 2,795 on Sunday. How many in all?
Answer 6281 people
Why 3,486 + 2,795 = 6,281.
Two Journeys: A trip of 1,258 km, then 2,647 km. How far in total?
Answer 3905 km
Why 1,258 + 2,647 = 3,905.