BuilderGrade 4⏱ 15 min
Measuring angles
Turn a ray, measure it with a protractor, name the angle, and see that angles add up.
Standards: 4.MD.C.54.MD.C.64.MD.C.7
1Wonder
A skateboarder does a “180” and ends up facing the other way. A “360” takes them all the way around. What are they counting?
2Explore
This activity needs a bigger screen
Turn your phone sideways, or open this lesson on a tablet or computer. The explanation and quiz below work here.
Try this
- Drag the orange point to make a right angle. What does the corner look like?
- Make an angle smaller than a right angle, then a bigger one. What are they called?
- Turn on Hide the number, guess an angle, then turn it off to check.
- Turn on Split it into two angles. Do the two parts always add up to the whole?
- Press Make an angle and try the challenges.
3Explain
Step 1 of 5
An angle is a turn
Two rays that start at the same point make an angle. The angle tells how far one ray is turned from the other.
Measuring angles
A full turn is 360°. A right angle is 90°. When an angle is split into parts, the parts add up to the whole angle.
4Practice
Question 1 of 5
What kind of angle is this?
5Recap
- An angle is a turn between two rays from the same point.
- Angles are measured in degrees. A full turn is 360°.
- Acute < 90°, right = 90°, obtuse between 90° and 180°, straight = 180°.
- Measure with a protractor: center on the point, one ray on 0, read the other ray.
- Angles add: the parts of a split angle add up to the whole.