Addition within 20
Number Line
Doubles Facts
Strategies
Do you agree?
100
8 + 5 =
13
100
Use this number line to solve 4 + 6 = ____.
10
100
Which of these are doubles facts?
2 + 2 = 4
3 + 4 = 7
4 + 4 = 8
6 + 6 = 12
2 + 2 =4
4 + 4 = 8
6 + 6 = 12
100
What does the strategy my way mean?
It means you solve the problem in a way that works best for you. You count on, use your fingers, use a number line, and more.
100
5 cats are running. 6 cats join them. How many cats are running now?
Mia says that there is 1 cat running, because 6 - 5 = 1. Do you agree or not agree?
Not agree, because you should add the two numbers. There are 11 running now.
200
9 + 6 =
15
200
Use this number line to solve 7 + 6 = ____.
13
200
5 + 5 =
10
200
Would you use doubles plus 1 or doubles plus 2 to solve this problem. Then solve the problem.
6 + 7 =
You would use doubles plus 1. It equals 13.
200
11 strawberries are in a basket. Jill eats 3 of them. How many are left?
Evan says that there are 7 left, because 11 - 3 = 7. Do you agree or not agree?
Not agree because 11 - 3 = 8.
300
10 + 4 =
14
300
Solve 6 + 5 on the open numberline.
11
300
8 + 8 =
16
300
Which strategies could you use to solve 5 + 7?
Doubles plus 2
Make a Ten
My Way
300
14 bowls sit in a bowl. 9 are green. The rest are purple. How many are purple?
Steve says 5 grapes are purple because 9 + 5 = 14. Do you agree or not agree with Steve?
Agree, because 5 and 9 equals 14.
400
Eric has 6 pretzels. His brother has 8 crackers. How many snacks do they have in all?
14 Snacks
400
Solve 8 + 7 on the open number line.
15
400
9 +9 =
18
400
Use make a ten to solve 9 + 5 = ____.
14
400
There are 16 pigs in the pen. 8 pigs run away. How many pigs are left?
Ms. Patterson says there are 24 left because 16 + 8 = 24. Do you agree or not agree?
Not agree, because the pigs ran away so there should be less than 16 left.
500
There are 9 squirrels in the park. 8 more join them. How many squirrels are at the park now? Write an equation to match the problem.
9 + 8 = 17
500
Solve 10 + 9 on the open number line.
19
500
Write a doubles fact and explain why it is a doubles fact.
Ex. 1 + 1 = 2
Because the two addends are the same.
500
Arielle made 7 cupcakes. Then she made 8 more. How many cupcakes did she make? Solve the problem and explain which strategy you used.
15. I used near doubles, make a ten, or my way.
500
There are 10 sharks. Some more swim up to them. Now there are 19 sharks. How many joined them?
Hunter says that 9 joined them because 10 + 9 = 19. Do you agree or not agree?
Agree, because the you know that one part is 10 and you don't know the other part. When you figure out the missing part, you find out that it is 9.