Palmdale School DistrictMathematics Content Standards

Grade 2NUMBER SENSE

Students:

2.1 understand and use the inverse relationship between addition and subtraction (e.g., an opposite number sentence for 8 + 6 = 14 is 14 - 6 = 8) to solve problems and check solutions.

Understanding the Fact Family relationship.

SUBTRACTIONADDITION

Fact Family 6, 8, & 14

6 + 8 = 14

8 + 6 = 14

14 - 6 = 8

14 - 8 = 6

We are starting with

A Total of Fourteen Apples

6 8 = 14

ADDITION

8 6 = 14

ADDITION

SUBTRACTION

14 6 = 8

SUBTRACTION

14 8 = 6

Understanding how to check your answers using Fact Families.

Defining Terms

Sum

Parts of an addition Problem

6 + 8 = 14

Addend Addend

We know that:

6 + 8 = 14

How To CheckADDITION PROBLEMS

With Subtraction

Check answer by subtracting an addend from the sum:

14 - 6

YOUR ANSWER SHOULD BE THE SECOND ADDEND!!!!

= 8

We know that:

8 + 6 = 14

How To CheckADDITION PROBLEMS

With Subtraction

Check answer by subtracting an addend from the sum:

14 - 8

YOUR ANSWER SHOULD BE THE SECOND ADDEND!!!!

= 6

Defining Terms

Difference

Parts of a subtraction Problem

14 - 6 = 8

Starting Number

Take Away Number

We know that:

14 - 6 = 8

How To CheckSUBTRACTION PROBLEMS

With Addition

Check answer by adding the answer to the take away number:

8 + 6

YOUR ANSWER SHOULD BE THE STRATING NUMBER!!!!

= 14

We know that:

14 - 8 = 6

How To CheckSUBTRACTION PROBLEMS

With Addition

Check answer by adding the answer to the take away number:

6 + 8

YOUR ANSWER SHOULD BE THE STRATING NUMBER!!!!

= 14

Practice Problems

EXAMPLEDirections: Make fact families

out of the given numbers.

Example: 2, 3, 5

3 + 2 = 5

2 + 3 = 5 5 - 2 = 3

5 - 3 = 2

GUIDED PRACTICEPart One

Directions: Make fact families out of the given numbers.

1) 4, 5, 9 2) 2, 5, 7

3) 4, 7, 11 4) 8, 9, 17

Reminder: four problems make up a fact family: two addition and two subtraction.

GUIDED PRACTICE ANSWERS

1) 4, 5, 94 + 7 = 11 11 - 4 = 7

7 + 4 = 11 11 - 7 = 4

2) 2, 5, 72 + 5 = 7 7 - 2 = 5

5 + 2 = 7 7 - 5 = 2

3) 4, 7, 114 + 7 = 11 11 - 4 = 7

7 + 4 = 11 11 - 7 = 4

4) 8, 9, 178 + 9 = 17 17 - 8 = 9

9 + 8 = 17 17 - 9 = 8

EXAMPLEDirections: Solve the given problem, then

check your answer using fact families.

Example: 5 + 4

5 + 4 = 9 9 - 5 = 4

Problem: Check:

Is the answer correct?Yes, because the check answer is the same as the other addend.

10 - 6 = 4 6 + 4 = 10

EXAMPLEDirections: Solve the given problem, then

check your answer using fact families.

Example: 10 - 6Problem: Check:

Is the answer correct?Yes, because the check answer is the same as the starting number.

GUIDED PRACTICEPart Two

Directions: Solve the given problem, then check your answer using fact families.

1) 7 + 6 = 2) 12 - 5 =

3) 9 + 4 = 4) 16 - 9 =

GUIDED PRACTICE ANSWERS

1) 7 + 6 = PROBLEM: 7 + 6 = 13

2) 12 - 5 =PROBLEM: 12 - 5 = 7

3) 9 + 4 =PROBLEM: 9 + 4 = 13

4) 16 - 9 =PROBLEM: 16 - 9 = 7

CHECK: 13 - 6 = 7 CHECK: 7 - 5 = 12

CHECK: 13 - 9 = 4 CHECK: 7 + 9 = 16