MATH UNIT: Place Value, Rounding, Addition and Subtraction

IN MATH: (We will start be studying concepts of Place Value, then move into a review of basic addition and subtraction skills, strategies, and facts. )

Vocabulary: 

 Place Value:  The value of where a digit is in a number.  In third grade we will focus on the place value from tenths through ten thousands.

Addend: A number being added

Difference: The answer obtained when you subtract two numbers

Sum: Total amount added. Total number of elements in the sets that were combined.

Estimate: A reasonable answer to an operation on numbers

Doubling: Adding the same amount twice; or, two times a number

Concepts:

There are four basic math operations: Addition, subtraction, multiplication, division.

Inverses are operations which undo each other… addition and subtraction.  Multiplication and division.

The Properties of Addition are:

Associative Property of Addition: When there are three addends, the sum does not change regardless of which two numbers you group together first. As in: 3 + 5 + 2 = (3 + 5) + 2 = 3 + (5 + 2) = 10; 8 + 2 = 3 + 7 = 10

Commutative Property of Addition: The order in which two numbers are added does not change the sum. As in: 9 + 7 = 16 and 7 + 9 = 16

Identity Property of Addition: When zero is added to any number, the sum is the original amount. Or, adding zero to any number does not change a number.

ENDURING UNDERSTANDINGS:  Subtraction has more than one meaning. It not only means the typical "take away" operation, but also can denote finding the difference between sets, such as, in a set of 2 red balloons and 6 green balloons, how many more balloons are green? What is the difference between the number of red and green balloons? (Diminution)Addition and subtraction are inverses; one undoes the other. Adding zero to a number or subtracting zero from a number does not change the original amount. Addition means the joining of two or more sets that may or may not be the same size. We can verify the results of our computation by using the inverse operation. Place value is crucial in operating on numbers. Estimation helps us see whether our answers are reasonable.

ESSENTIAL QUESTIONS: How are addition and subtraction different? In why type of situations do we subtract? In what type of situations do we add? What are some ways we use estimation in everyday life? Why is place value important? How is zero different from any other whole number you might add or subtract? How do we use addition and subtraction to tell number stories? How are addition and subtraction alike?