Cogito
Grade 4 Math · Chapter 7 · Lesson 1
An Angle Is a Turn
Longer arms do not make a bigger angle.
10 problems · about 14 minutes · 4.MD.C.5
What this lesson teaches
The child understands an angle as an amount of turn between two rays, measured in degrees.
- An angle is the turn between two lines from one point.
- It is measured in degrees. A full turn is 360.
- Longer arms do not make a bigger angle.
Warm-Up Review
From earlier lessons. Loosen up before the new work.
2 problemsReview — Decimals and Money: How many cents is $0.35?
Answer 35
Why 35 cents.
Review — Adding Tenths and Hundredths: 7/10 + 15/100. How many hundredths?
Answer 85
Why 85/100, written 0.85.
Warm Up
Straightforward practice. Get the method working first.
4 problemsHow many degrees is a half turn?
Answer 180
Why 180 degrees, a straight line.
What is an angle?
Answer The amount of turn between two lines.
Why An angle is a turn. Arm length has nothing to do with it.
How many degrees in a half turn?
Answer 180
Why Two right angles.
How many right angles in a full turn?
Answer 4
Why 4 × 90 = 360.
Build It Up
The same ideas with more to keep track of.
2 problemsDoes making the arms longer change the angle?
Answer No. The turn is the same.
Why You saw the number stay put.
How many degrees in three quarters of a turn?
Answer 270
Why 3 × 90.
Stretch Yourself
Mixed problems. Work out what kind of question it is before you start.
2 problemsThe Corner: How many degrees is a right angle?
Answer 90 degrees
Why 90 degrees.
The Full Turn: How many degrees in a full turn all the way round?
Answer 360 degrees
Why 360 degrees.