Cogito
Grade 1 Math · Chapter 4 · Lesson 5
Breaking Teen Numbers Apart
Split a teen number into ten and the rest.
10 problems · about 11 minutes · 1.NBT.B.2.b, 1.OA.C.6
What this lesson teaches
The child decomposes a teen number into 10 + n using a number bond.
- A teen number always splits into 10 and some ones.
- The ten part never changes.
- Only the ones part is different each time.
Warm-Up Review
From earlier lessons. Loosen up before the new work.
5 problemsReview — Writing Teen Numbers: In 16, how many ones are there?
Answer 6
Why 16 is one ten and 6 ones.
Review — Saying It the Ten Way: Ten five is which number?
Answer 15
Why Ten five is fifteen.
Review — Ten and Some More: 10 + 2 = ?
Answer 12
Why 10 + 2 = 12.
Review — Ten Ones Make One Ten: How many ones are in one ten?
Answer 10
Why One ten is made of ten ones.
Review — Adding and Subtracting to Ten: 7 − 2 = ?
Answer 5
Why 7 − 2 = 5.
Warm Up
Straightforward practice. Get the method working first.
3 problems12 is 10 and what?
Answer 2
Why 12 is 10 and 2.
16 is 10 and what?
Answer 6
Why 16 is 10 and 6.
14 is 10 and what?
Answer 4
Why Ten four.
Build It Up
The same ideas with more to keep track of.
1 problem19 is 10 and what?
Answer 9
Why Ten nine.
Stretch Yourself
Mixed problems. Work out what kind of question it is before you start.
1 problemSplitting Sweets: Mia has 17 sweets. She puts 10 in a bag. How many are left out?
Answer 7 sweets
Why 17 is 10 and 7.