2-min Fluency Warm-up — Mental math.
42 + 10 =
75 − 10 =
36 + 10 =
88 − 10 =
New Skill: Adding 3 Numbers
When adding 3 numbers, add the first two, then add the third.
25 + 10 + 20
Step 1: 25 + 10 = 35
Step 2: 35 + 20 = 55
Answer: 55
30 + 15 + 5
Step 1: 30 + 15 = 45
Step 2: 45 + 5 = 50
Answer: 50
Fill in the blanks. Add the first two numbers, then add the third.
12 + 20 + 30
First: 12 + 20 =
Then: + 30 =
15 + 5 + 25
First: 15 + 5 =
Then: + 25 =
40 + 10 + 8
First: 40 + 10 =
Then: + 8 =
33 + 7 + 20
First: 33 + 7 =
Then: + 20 =
Number Talk — Without calculating, which order is EASIER? Explain.
A: 15 + 20 + 5
B: 15 + 5 + 20
My thinking:
A: 28 + 12 + 35
B: 35 + 28 + 12
My thinking:
Read carefully. There are THREE numbers in this problem.
You found 12 shells on the beach. Your sister found 8 shells. Your brother found 15 shells. How many shells did you all find together?
Draw or write your thinking:
shells