RANGER Math practice · Geometry · ages 10+
Free missing angles practice
Ranger's Math Trail practices the three angle facts you use most: angles on a straight line add to 180°, angles that make a right angle add to 90°, and the three angles of a triangle add to 180°.
Each answer names the rule (supplementary or complementary) and does the subtraction.
Pick a level
Free, no sign-up. The game asks your age once, then every answer comes with a hint and a step-by-step Show me how.
How to do it
- Angles on a straight line add up to 180° (supplementary angles).
- Angles that make a right angle add up to 90° (complementary angles).
- The three angles inside any triangle add up to 180°.
- Subtract the angles you know from the total to find the missing one.
Worked examples
Example 1Two angles make a straight line. One is 125°. What is the other?
- Angles on a straight line add up to 180° (supplementary).
- 180 − 125 = 55°.
Answer: 55°
Try one like it →Example 2A triangle has angles of 94° and 32°. What is the third angle?
- The three angles of a triangle always add up to 180°.
- 94 + 32 = 126.
- 180 − 126 = 54°.
Answer: 54°
Try one like it →Mistakes to watch for
- Add the known angles first, then subtract once: 180 − (65 + 40) = 75.
- A right angle is marked with a small square in the corner.
The game
Questions
Do I type the degree sign?
No. Type the number and the game adds the °.
What age is it for?
Usually grades 4 to 7 (ages 10 to 12).
More math practice: Addition · Subtraction · Multiplication facts · Division and long division · Place value and rounding · Fractions · Decimals · Percents and ratios · Negative numbers · Order of operations · Exponents and square roots · Solving equations · Slope and linear equations · Systems of equations · Factoring quadratics · Area, perimeter and volume · Pythagorean theorem · Circles · Mean, median, mode and range · All math topics