Week 7MondayAdding Tens (Mental Math)
1Add 10

When you add 10, only the tens digit changes. The ones stay the same.

23 + 10 =

45 + 10 =

67 + 10 =

12 + 10 =

2Add Multiples of 10

Add the tens. Keep the ones.

34 + 20 =

56 + 30 =

78 + 10 =

42 + 50 =

3Number Line Jumps

Use the number line. Mark jumps of 10 from the first number.

25 + 30 =

20
30
40
50
60
70
80

Mark jumps of 10 starting at 25

47 + 40 =

40
50
60
70
80
90
100

Mark jumps of 10 starting at 47

4Number Talk: Which is Bigger?

Number Talk — Which sum is bigger? Explain WITHOUT calculating.

34 + 20 or 34 + 30

My thinking:

56 + 10 or 56 + 40

My thinking:

5Challenge: Three Numbers

Challenge — Add all the tens first, then all the ones.

20 + 30 + 45 =

10 + 50 + 23 =