MMati Learning Hub

TOPIC 7 · GRADE 4 FOUNDATION

Measure, Split, and Combine Angles

Estimate and measure angles, then use addition or subtraction to find missing parts.

MA.4.GR.1.2–MA.4.GR.1.3

BIG IDEA

Angle measure is additive: non-overlapping smaller angles combine to make the whole angle.

WHAT TO KNOW

  • Use benchmark angles such as 30°, 45°, 60°, 90°, and 180° to estimate first.
  • Place a protractor's center on the vertex and its zero line on one ray.
  • If a 75° angle is split into 30° and an unknown angle, then 30° + ? = 75°, so ? = 45°.

WATCH OUT

Read the protractor scale that begins at the ray aligned with zero; the other scale runs backward.

TRY IT

Change the whole angle and the known part to see the matching addition and subtraction equations.

Choose the next topic from the lesson rail when you are ready.