CCSS.Math.Content.4.MD.C.5a
The Standard
An angle is measured with reference to a circle with its center at the common endpoint of the rays, by considering the fraction of the circular arc between the points where the two rays intersect the circle. An angle that turns through 1/360 of a circle is called a "one-degree angle," and can be used to measure angles.
Common Core State Standards for Mathematics
Teacher's field guide
What This Standard Means
What Students Need to Do
- Students connect angle size to the amount of turn between two rays. They use a full turn of 360 degrees to reason about smaller turns and angle measures.
What Mastery Looks Like
- Students identify a degree as a unit based on dividing a full turn into 360 equal parts. They find familiar angle measures from halves, fourths, and other equal parts of a circle.
Common Misconceptions
- Students may think longer rays make a larger angle. They may use the arc length instead of the fraction of the full turn. Some confuse a one-degree turn with one of 100 equal parts.
How to Assess It
- Show a circle divided into eight equal sectors with one sector shaded. Ask, “What is the shaded angle measure, and how does 360 help you know?”
Lesson moves
Ways to Teach It
Cut paper circles into halves, fourths, and eighths, then place two straws from the center to model each angle.
Ask students to explain why a quarter turn measures 90 degrees, using a labeled circle in their response.
Play Angle Match by pairing cards showing circle fractions, turns, and degree measures such as one-half, half turn, and 180 degrees.
Examine clock hands at 3:00, 6:00, and 9:00, then connect each turn from 12 to its angle measure.
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Printable 4.MD.C.5a Worksheet
A ready-to-print activity worksheet aligned to CCSS.Math.Content.4.MD.C.5a, with an answer key for the teacher on its own page. No account needed.
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Related Standards
- CCSS.Math.Content.HSF-TF.A.1
Understand radian measure of an angle as the length of the arc on the unit circle subtended by the angle.
- CCSS.Math.Content.8.G.A.1b
Angles are taken to angles of the same measure.
- CCSS.Math.Content.4.MD.C.5
Recognize angles as geometric shapes that are formed wherever two rays share a common endpoint, and understand concepts of angle measurement:
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