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Palmdale School District
Mathematics Content Standards
Grade 2
NUMBER 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.
Fact Family
6, 8, & 14
ADDITION
SUBTRACTION
6 + 8 = 14
14 - 6 = 8
8 + 6 = 14
14 - 8 = 6
We are starting with
A Total of Fourteen Apples
ADDITION
6
8
= 14
ADDITION
8
6 = 14
SUBTRACTION
14
6= 8
SUBTRACTION
14
8= 6
Understanding how to check your
answers using Fact Families.
Defining Terms
Parts of an addition Problem
Addend
Addend
6 + 8 = 14
Sum
How To Check
ADDITION PROBLEMS
With Subtraction
We know that:
6 + 8 = 14
Check answer by
subtracting an
addend from the
sum:
14 - 6 = 8
YOUR ANSWER SHOULD BE THE SECOND ADDEND!!!!
How To Check
ADDITION PROBLEMS
With Subtraction
We know that:
8 + 6 = 14
Check answer by
subtracting an
addend from the
sum:
14 - 8 = 6
YOUR ANSWER SHOULD BE THE SECOND ADDEND!!!!
Defining Terms
Parts of a subtraction Problem
Starting
Number
Take Away
Number
14 - 6 = 8
Difference
How To Check
SUBTRACTION PROBLEMS
With Addition
We know that:
14 - 6 = 8
Check answer by adding
the answer to the take
away number:
8 + 6 = 14
YOUR ANSWER SHOULD BE THE STRATING NUMBER!!!!
How To Check
SUBTRACTION PROBLEMS
With Addition
We know that:
14 - 8 = 6
Check answer by adding
the answer to the take
away number:
6 + 8 = 14
YOUR ANSWER SHOULD BE THE STRATING NUMBER!!!!
Practice Problems
EXAMPLE
Directions: Make fact families
out of the given numbers.
Example:
2, 3, 5
2+3=5
5- 2=3
3+2=5
5- 3=2
GUIDED PRACTICE
Part One
Directions: Make fact families out of the given
numbers.
Reminder: four problems make up a fact
family: two addition and two subtraction.
1) 4, 5, 9
2) 2, 5, 7
3) 4, 7, 11
4) 8, 9, 17
GUIDED PRACTICE ANSWERS
1) 4, 5, 9
2) 2, 5, 7
4 + 7 = 11
11 - 4 = 7
2+5=7
7-2=5
7 + 4 = 11
11 - 7 = 4
5+2=7
7-5=2
3) 4, 7, 11
4) 8, 9, 17
4 + 7 = 11
11 - 4 = 7
8 + 9 = 17
17 - 8 = 9
7 + 4 = 11
11 - 7 = 4
9 + 8 = 17
17 - 9 = 8
EXAMPLE
Directions: Solve the given problem, then
check your answer using fact families.
Example:
5+4
Problem:
Check:
5+4 =9
9-5=4
Is the answer correct?
Yes, because the check answer is the
same as the other addend.
EXAMPLE
Directions: Solve the given problem, then
check your answer using fact families.
Example:
10 - 6
Problem:
Check:
10 - 6 = 4
6 + 4 = 10
Is the answer correct?
Yes, because the check answer is the
same as the starting number.
GUIDED PRACTICE
Part 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 =
2) 12 - 5 =
PROBLEM:
7 + 6 = 13
PROBLEM:
CHECK:
13 - 6 = 7
CHECK:
3) 9 + 4 =
12 - 5 = 7
7 - 5 = 12
4) 16 - 9 =
PROBLEM:
9 + 4 = 13
PROBLEM:
CHECK:
13 - 9 = 4
CHECK:
16 - 9 = 7
7 + 9 = 16