All the solutions provided in McGraw Hill Math Grade 2 Answer Key PDF Chapter 1 Lesson 5 Add Three Numbers will give you a clear idea of the concepts.

Explore and Explain Teacher Directions: Have students use counters to show the following: There are 4 fish, 6 frogs, and 2 snakes in the pond. Trace the counters and write how many in all.
Explanation: See and Show

You can group addends in different ways. The sum will stay the same. Look for facts you know.

Find each sum. Circle the numbers you add first. Write that sum in the box.

Question 1.
2 + 4 + 2 = _____  Explanation:
If we add the addends in different ways also the sum will be the same.
2 + 4 = 6
6 + 2 = 8

Question 2.
9 + 1 + 2 = _____  Explanation:
If we add the addends in different ways also the sum will be the same.
9 + 1 = 10
10 + 2 = 12

Question 3.
7 + 4 + 7 = _____  Explanation:
If we add the addends in different ways also the sum will be the same.
7 + 7 = 14
14 + 4 = 18

Question 4.
2 + 7 + 8 = _____  Explanation:
If we add the addends in different ways also the sum will be the same.
7 + 2 = 9
9 + 8 = 17

Question 5.
3 + 7 + 4 = _____  Explanation:
If we add the addends in different ways also the sum will be the same.
7 + 3 = 10
10 + 4 = 14

Question 6.
5 + 3 + 5 = _____  Explanation:
If we add the addends in different ways also the sum will be the same.
5 + 5 = 10
10 + 3 = 13

Talk Math How do you decide which two numbers to add first when adding three digits?
First we try to make 10

Add two numbers first. Look for facts you know.

On My Own

Find each sum. Circle the numbers you add first. Write that sum in the box.

Question 7.
4 + 3 + 4 = _____  Explanation:
If we add the addends in different ways also the sum will be the same.
4 + 4 = 8
8 + 3 = 11

Question 8.
4 + 3 + 7 = _____  Explanation:
If we add the addends in different ways also the sum will be the same.
7 + 3 = 10
10 + 4 = 14

Question 9.
2 + 8 + 3 = _____  Explanation:
If we add the addends in different ways also the sum will be the same.
8 + 2 = 10
10 + 3 = 13

Question 10.
6 + 1 + 6 = ____ Explanation:
If we add the addends in different ways also the sum will be the same.
6 + 6 = 12
12 + 1 = 13

Find each sum.

Question 11.
5 + 5 + 5 = ____ Explanation:
If we add the addends in different ways also the sum will be the same.
5 + 5 = 10
10 + 5 = 15

Question 12.
6 + 6 + 3 = ____ Explanation:
If we add the addends in different ways also the sum will be the same.
6 + 6 = 12
12 + 3 = 15

Question 13.
7 + 4 + 7 = ___ Explanation:
If we add the addends in different ways also the sum will be the same.
7 + 7 = 14
14 + 4 = 18

Question 14.
9 + 8 + 1 = ____ Explanation:
If we add the addends in different ways also the sum will be the same.
9 + 1 = 10
10 + 8 = 18

Question 15.
1 + 7 + 3 = ____ Explanation:
If we add the addends in different ways also the sum will be the same.
7 + 3 = 10
10 + 1 = 11

Question 16.
5 + 7 + 5 = ____ Explanation:
If we add the addends in different ways also the sum will be the same.
5 + 5 = 10
10 + 7 = 7

Question 17.  Explanation:
If we add the addends in different ways also the sum will be the same.
7 + 3 = 10
10 + 5 = 15

Question 18.  Explanation:
If we add the addends in different ways also the sum will be the same.
7 + 7 = 14
14+ 1 = 15

Question 19.  Explanation:
If we add the addends in different ways also the sum will be the same.
9 + 1 = 10
10 + 8 = 18

Problem Solving

Question 20.
The zoo has 5 black bears, 5 brown bears and 2 polar bears. How many bears are at the zoo? ____ bears
12 bears
Explanation:
The zoo has 5 black bears,
5 brown bears and 2 polar bears.
5 + 5 = 10
10 + 2 = 12
12 bears are at the zoo.

Question 21.
Lisa saw 4 sheep and 4 goats at the petting zoo. She also saw 3 piglets. How many animals did Lisa see at the petting zoo?
____ animals
Write the doubles fact that helped you solve the problem.
____ + ____ = _____