Cogito
Grade 2 Math · Chapter 1 · Lesson 1
Doubles
Two equal groups make a double.
8 problems · about 11 minutes · 2.OA.B.2
What this lesson teaches
The child recalls doubles facts to 10 + 10 and recognizes a double as two equal addends.
- A double adds a number to itself.
- Doubles are easy to picture, so they are easy to remember.
- Every double gives an even answer.
Warm Up
Straightforward practice. Get the method working first.
4 problems7 + 7 = ?
Answer 14
Why 7 + 7 = 14.
Which of these is a double?
Answer 9 + 9
Why Only 9 + 9 has two equal parts.
5 + 5 = ?
Answer 10
Why Two hands of five.
6 + 6 = ?
Answer 12
Why One egg box holds 12.
Build It Up
The same ideas with more to keep track of.
2 problems8 + 8 = ?
Answer 16
Why Double 8.
10 + 10 = ?
Answer 20
Why Two full tens.
Stretch Yourself
Mixed problems. Work out what kind of question it is before you start.
2 problemsTwo Hands: Leo has 8 marbles in each hand. How many marbles does he have altogether?
Answer 16 marbles
Why 8 + 8 = 16.
Twin Bookshelves: Two shelves each hold 9 books. How many books are on the shelves in all?
Answer 18 books
Why 9 + 9 = 18.