# 3.3 Wrapping Up Addition and Subtraction Within 1,000

## Unit Goals

• Students use place value understanding to round whole numbers and add and subtract within 1,000. They also represent and solve two-step word problems using addition, subtraction, and multiplication and assess the reasonableness of answers.

### Section A Goals

• Fluently add within 1,000 using algorithms based on place value and properties of operations.
• Use place value understanding to compose and decompose numbers.

### Section B Goals

• Fluently subtract within 1,000 using algorithms based on place value, properties of operations, and the relationship between addition and subtraction.

### Section C Goals

• Round whole numbers to the nearest multiple of 10 and 100.

### Section D Goals

• Assess the reasonableness of answers.
• Solve two-step word problems using addition, subtraction, and multiplication.

### Glossary Entries

• algorithm
A set of steps that works every time as long as the steps are carried out correctly.

• area

The number of square units that cover a flat figure without gaps or overlaps.

• array

An arrangement of objects in rows and columns. Each column must contain the same number of objects as the other columns, and each row must have the same number of objects as the other rows.

• bar graph
A way to show how many in each group or category using the length of rectangles.

• equation

A statement that includes an equal sign (=). It tells us that what is on one side of the sign is equal to what is on the other side.

• expanded form

A specific way of writing a number as a sum of hundreds, tens, and ones.

Expanded form writes a number as a sum of the value of each digit. Example: 482 written in expanded form is $$400 + 80 + 2$$ .

• expression

An expression has at least 2 numbers and at least one math operation (such as addition, subtraction, multiplication and division).

• factor
When we multiply two whole numbers to get a product, each of those numbers is a factor of the product.

• key
The part of a picture graph that tells what each picture represents.

• multiplication
The operation that tells you the total number of objects when you have a certain number of equal groups.

• parentheses
Grouping symbols that can be used in expressions or equations, such as: $$(3 \times 5) + (2 \times 5), (24 \div 2) + 5 = 17$$.

• picture graph
A way to show how many in each group or category using pictures of the objects or symbols.

• product
The result of multiplying some numbers.

• rounding

A formal way to say which number a given number is closer to. For example, for 182, the number 180 is the closest multiple of ten and 200 is the closest multiple of a hundred. We can round 182 to 180 (if rounding to the nearest ten) or 200 (if rounding to the nearest hundred).

• scaled bar graph
A bar graph marked in multiples of some number other than 1.

• scaled picture graph
A picture graph where each picture represents an amount other than 1.

• square centimeter

A square with side lengths of 1 centimeter.

• square foot

A square with side lengths of 1 foot.

• square inch
A square with side lengths of 1 inch.

• square meter
A square with side lengths of 1 meter.