Cogito
Grade 2 Math · Chapter 4 · Lesson 1
Adding With Place Value
Tens with tens, ones with ones.
10 problems · about 11 minutes · 2.NBT.B.5
What this lesson teaches
The child adds two two-digit numbers within 100 by adding like units, with no new ten needed.
- Add the tens to the tens.
- Add the ones to the ones.
- Then say the answer as tens and ones.
Warm-Up Review
From earlier lessons. Loosen up before the new work.
2 problemsReview — A Hundred More, A Hundred Less: A hundred more than 546 is?
Answer 646
Why 546 + 100 = 646.
Review — Ten More, Ten Less: Ten more than 236 is?
Answer 246
Why 236 + 10 = 246.
Warm Up
Straightforward practice. Get the method working first.
4 problems23 + 41 = ?
Answer 64
Why 23 + 41 = 64.
What goes with the tens?
Answer Other tens.
Why Like units go together.
34 + 25 = ?
Answer 59
Why 5 tens, then 4 and 5.
52 + 36 = ?
Answer 88
Why 8 tens, then 2 and 6.
Build It Up
The same ideas with more to keep track of.
2 problems61 + 27 = ?
Answer 88
Why 8 tens, then 1 and 7.
45 + 30 = ?
Answer 75
Why The 5 stays put.
Stretch Yourself
Mixed problems. Work out what kind of question it is before you start.
2 problemsTwo Classes: One class collected 32 tins and another collected 46. How many tins in all?
Answer 78 tins
Why 32 + 46 = 78.
The Long Walk: Leo walked 51 metres, then 24 metres more. How far did he walk?
Answer 75 metres
Why 51 + 24 = 75.