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Cogito

Grade 7 Math · Chapter 8 · Lesson 4

Practice Worksheet

When Three Measurements Fix a Triangle

One triangle, many, or none at all.

10 problems · about 19 minutes · 7.G.A.2

NameDate

Figure — use these to answer the problems

Two angles of a triangle. The third is whatever is left of 180°.
030609012015018040° + 60° = 100°
First angle40
Second angle60
Figure 1

Warm-Up Review

From earlier lessons. Loosen up before the new work.

3 problems

  1. From “Angle Pairs”

    Supplement of 130°?

    Answer

  2. From “Volume and Surface Area of Prisms”

    Base area 18, height 7. Volume?

    Answer

  3. From “Angle Pairs”

    Supplementary to 47?

    Answer

Warm Up

Straightforward practice. Get the method working first.

3 problems

  1. Can sides 4, 4 and 9 make a triangle? 1 for yes, 0 for no.

    Answer

  2. Angles 30° and 90°. What is the third?

    Answer

  3. Can sides 5, 6 and 10 make a triangle? 1 for yes, 0 for no.

    Answer

Build It Up

The same ideas with more to keep track of.

2 problems

  1. Can sides 1, 2 and 8 make a triangle? 1 for yes, 0 for no.

    Answer

  2. Do three given angles fix the size of a triangle? 1 for yes, 0 for no.

    Answer

Stretch Yourself

Mixed problems. Work out what kind of question it is before you start.

2 problems

  1. The Third Angle

    A triangle has angles of 50° and 60°. What is the third, in degrees?

    Answer

  2. The Impossible Triangle

    Can sides 2, 3 and 9 make a triangle? Answer 1 for yes, 0 for no.

    Answer