Cogito
Grade 7 Math · Chapter 8 · Lesson 3
Angle Pairs
Angles that add to 90 or to 180.
10 problems · about 18 minutes · 7.G.B.5
What this lesson teaches
The child uses complementary, supplementary, and vertical angle relationships to find an unknown angle.
- Complementary angles add to 90°; supplementary angles add to 180°.
- Angles on a straight line are supplementary.
- Where two lines cross, opposite angles are equal.
Warm-Up Review
From earlier lessons. Loosen up before the new work.
3 problemsReview — Volume and Surface Area of Prisms: Base area 18, height 7. Volume?
Answer 126
Why 126.
Review — Angle Pairs: Supplementary to 47?
Answer 133
Why 133 degrees.
Review — Telling Area from Circumference: Edging a round rug. 1 for circumference, 2 for area.
Answer 1
Why Circumference.
Warm Up
Straightforward practice. Get the method working first.
3 problemsSupplement of 130°?
Answer 50
Why 50°.
Complement of 40°?
Answer 50
Why 90 − 40.
Supplement of 65°?
Answer 115
Why 180 − 65.
Build It Up
The same ideas with more to keep track of.
2 problemsTwo lines cross at 55°. What is the vertical angle?
Answer 55
Why Opposite angles are equal.
That same crossing. What is the angle next to the 55°?
Answer 125
Why On a straight line.
Stretch Yourself
Mixed problems. Work out what kind of question it is before you start.
2 problemsThe Complement: An angle is 25°. What is its complement, in degrees?
Answer 65
Why 65°.
The Supplement: An angle is 110°. What is its supplement, in degrees?
Answer 70
Why 70°.