# 2.7 Adding and Subtracting within 1,000

## Unit Goals

• Students use place value understanding, the relationship between addition and subtraction, and properties of operations to add and subtract within 1,000.

### Section A Goals

• Add and subtract numbers within 1,000 without composition or decomposition, and use strategies based on the relationship between addition and subtraction and the properties of operations.

### Section B Goals

• Add numbers within 1,000 using strategies based on place value understanding, including composing a ten or hundred.

### Section C Goals

• Subtract numbers within 1,000 using strategies based on place value understanding, including decomposing a ten or hundred.

### Glossary Entries

• a third

One piece of a shape split into 3 pieces that are the same size.

A third of the rectangle is shaded.

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

• centimeter

A length unit in the metric measurement system. There are 100 centimeters in a meter.

• compose
To make a new unit from 10 of the next smallest unit. For example, compose a ten from 10 ones.

• data
Information about the things or people in a group.

Example: If you have a box of colored pencils, then the lengths and colors of each of the pencils are data about the pencils in the box.

• decompose
To break a unit into 10 of the next smallest unit.  For example, decompose a ten into 10 ones.

• 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 $$400 + 80 + 2$$ .

• face
A flat side of a solid shape.

• foot

A length unit in the U.S. customary measurement system.

There are 12 inches in a foot.

• hexagon

A shape with 6 sides and 6 corners.

• inch

A length unit in the U.S. customary measurement system.

There are 12 inches in a foot.

• line plot
A way to show how many of each measurement using an x for each measurement.

• meter

A length unit in the metric measurement system.

There are 100 centimeters in a meter.

• number line

A diagram that represents numbers as lengths from 0 using equally spaced tick marks or points.

• pentagon
A shape with 5 sides and 5 corners.

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