Finding Unknown Angles Worksheets

Free printable worksheets with answer keys. Pick a level, preview the questions, then open the sheet to swap or delete any single question.

Grade 4CCSS 4.MD.C.7Answer key includedPDF · Print

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Easy: Two angles in a right angle

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Worksheet variations

Angles that share a vertex and don't overlap add up. A right angle, marked with a small square, is 90°; a straight line is 180°. Subtract the known angles from the whole to find the unknown one.

EasyTwo angles in a right angle MediumTwo angles on a straight line HardThree angles in a right or straight angle

How to solve it: a worked example

Find the unknown angle.

Start
A right angle is 90°
Answer

Common mistakes to watch for

Subtracting from 180° when the whole is a right angle, or from 90° when it is a straight line.
Subtracting only one of two known angles.
Measuring the picture instead of using the numbers.

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