palmdale school district mathematics content standards grade 2 number sense students: 2.1 understand...
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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.
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
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 =