Angles
An angle is formed by two rays with a common endpoint called the vertex.
Angle Types
- Acute Angle: Measures less than 90°.
- Right Angle: Measures exactly 90°.
- Obtuse Angle: Measures more than 90° but less than 180°.
- Straight Angle: Measures exactly 180°.
- Reflex Angle: Measures more than 180° but less than 360°.
Angle Measurement
Angles are measured in degrees (°).
Angle Pairs
- Complementary Angles: Add up to 90°.
- Supplementary Angles: Add up to 180°.
- Vertical Angles: Opposite angles formed by intersecting lines, congruent.
Angle Notation
Angles are typically represented by a three-letter notation, e.g., ∠ABC.
.◂Math Worksheets and Study Guides Fourth Grade. Perimeter
Study Guide
Perimeter 
Activity Lesson
Perimeter Activity Lesson
Polygon Perimeter Activity Lesson
Amazing Areas Worksheet/Answer key
Perimeter Worksheet/Answer key
Perimeter Worksheet/Answer key
Perimeter Worksheet/Answer key
Dot to Dot Worksheet/Answer key
Triangle Inequality Theorem Worksheet/Answer key
Park Perimeter Worksheet/Answer key
Polygon Perimeters Vocabulary/Answer key
Perimeter
Activity LessonActivity LessonActivity LessonWorksheet/Answer keyWorksheet/Answer keyWorksheet/Answer keyWorksheet/Answer keyWorksheet/Answer keyWorksheet/Answer keyWorksheet/Answer keyVocabulary/Answer keyThe resources above cover the following skills:
Geometry (NCTM)
Analyze characteristics and properties of two- and three-dimensional geometric shapes and develop mathematical arguments about geometric relationships.
Identify, compare, and analyze attributes of two- and three-dimensional shapes and develop vocabulary to describe the attributes.
Use visualization, spatial reasoning, and geometric modeling to solve problems.
Use geometric models to solve problems in other areas of mathematics, such as number and measurement.