Worked examples
Two examples
Example 1
Two angles of a triangle are 50° and 70°. What is the third?
- The three add to 180°: 180 − 50 − 70.
Answer: 60°
Example 2
An isosceles triangle has two equal angles of 40° each. What is the third?
- 180 − 40 − 40.
Answer: 100°
Where this is taught: Quiz 36: Angles, “The three angles of a triangle add to 180”
The drill
Ten problems
This drill also has challenge problems. They use the same skill, set up the way the GED test sometimes sets up a problem, so that it looks new at first.
How many:
Type each answer, then press Check my answers at the bottom. Commas in large numbers are fine.Write each answer on the line. The answer key, with the reasoning, is on the last page.