Cogito
Grade 2 Math · Chapter 4 · Lesson 9
Word Problems Within 100
Draw the bars, then choose what to do.
10 problems · about 13 minutes · 2.OA.A.1
What this lesson teaches
The child solves one-step add-to, take-from, put-together, and compare problems within 100.
- Draw the bars before choosing what to do.
- A missing whole means add. A missing part means subtract.
- In a compare problem nothing changes.
Warm-Up Review
From earlier lessons. Loosen up before the new work.
2 problemsReview — Checking by Adding: 75 − 38 = ?
Answer 37
Why 75 − 38 = 37, and 37 + 38 = 75.
Review — Subtracting With a Broken Ten: 45 − 28 = ?
Answer 17
Why 45 − 28 = 17.
Warm Up
Straightforward practice. Get the method working first.
3 problems47 birds. 28 fly away. How many are left?
Answer 19
Why 47 − 28 = 19.
In a compare problem, does anything join or leave?
Answer No. Two amounts just sit side by side.
Why Comparing finds the difference without changing anything.
52 and 39 put together. How many?
Answer 91
Why Both parts known.
Build It Up
The same ideas with more to keep track of.
1 problem80 take away 46. How many are left?
Answer 34
Why Break a ten.
Stretch Yourself
Mixed problems. Work out what kind of question it is before you start.
4 problems63 and 48. How much more is 63?
Answer 15
Why A compare problem.
The Playground: 38 children were outside and 25 more came out. How many are outside now?
Answer 63 children
Why 38 + 25 = 63.
Comparing Collections: Ana has 46 stickers and Leo has 29. How many more does Ana have?
Answer 17 more
Why 46 − 29 = 17.
The Missing Start: After 26 more books arrived, a shelf held 71. How many were there before?
Answer 45 books
Why 71 − 26 = 45.