Cogito
Grade 1 Math · Chapter 10 · Lesson 8
When You Need a New Ten
Make a new ten with bigger numbers too.
10 problems · about 14 minutes · 1.NBT.C.4
What this lesson teaches
The child adds within 100 where the ones compose a new ten, and writes down what happened.
- When the ones reach ten, bundle them.
- The new ten joins the other tens.
- Write the answer down and check it.
Warm-Up Review
From earlier lessons. Loosen up before the new work.
4 problemsReview — Adding to 100 With Place Value: 34 + 25 = ?
Answer 59
Why 5 tens and 9 ones is 59.
Review — Ten More, Ten Less to 100: Ten more than 66 is?
Answer 76
Why 6 tens became 7 tens.
Review — Comparing Numbers to 100: Which is greater, 38 or 41?
Answer 41
Why 41 has more tens.
Review — Counting to 120: What comes right after 104?
Answer 105
Why After 104 comes 105.
Warm Up
Straightforward practice. Get the method working first.
3 problems29 + 34 = ?
Answer 63
Why 5 tens and 13 ones becomes 6 tens and 3 ones.
What do you check before adding the tens?
Answer Whether the ones reach ten.
Why Checking the ones tells you whether a new ten is needed.
46 + 27 = ?
Answer 73
Why 6 and 7 is 13.
Build It Up
The same ideas with more to keep track of.
1 problem35 + 28 = ?
Answer 63
Why 5 and 8 is 13.
Stretch Yourself
Mixed problems. Work out what kind of question it is before you start.
2 problems42 + 31 = ?
Answer 73
Why 2 and 1 is only 3.
Two Piles of Books: 27 books on one shelf and 46 on another. How many?
Answer 73 books
Why 27 + 46 = 73.