CCSS.Math.Content.4.MD.C.5b
The standard
An angle that turns through n one-degree angles is said to have an angle measure of n degrees.
Common Core State Standards for Mathematics
What this standard means
Students need to understand degrees as units for measuring turns. One degree is a tiny equal turn, and an angle’s measure tells how many of those one-degree turns fit from one ray to the other. They should connect angle size to amount of turn, not to the length of the rays.
Mastery looks like explaining that a 45 degree angle is made of 45 one-degree turns and that a larger turn has a larger measure. Students often think longer rays mean bigger angles, or they confuse the space inside an angle with the turn that created it.
Ways to teach it
- Have students use two craft sticks joined with a brad to build angles and compare which shows a bigger turn.
- Ask students to explain why lengthening both rays of a 30 degree angle does not make the angle bigger.
- Show three drawn angles and ask students to circle the one that represents the greatest turn and explain why.
- Connect angles to a clock by asking what turn the minute hand makes from 12 to 3.
Plan a lesson for CCSS.Math.Content.4.MD.C.5b
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Related standards
- CCSS.Math.Content.4.MD.C
Geometric measurement: understand concepts of angle and measure angles.
- CCSS.Math.Content.4.MD.C.6
Measure angles in whole-number degrees using a protractor. Sketch angles of specified measure.
- CCSS.Math.Content.8.G.A.1b
Angles are taken to angles of the same measure.
- CCSS.Math.Content.4.MD.C.5a
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 ...