Let's practise


What is the size of angle n?
n =°

  • Read the question and then read it again. What is it asking you to do?
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It is asking you to work out the size of angle n.

  • What angle sizes do you already know?
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One angle is 65° and another is a right angle. That is the same as 90°.

  • What do you know about the sum of angles in a triangle?
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Angles in a triangle add up to 180°.

  • To calculate the size of the missing angle, subtract the size of the angles you do know from 180°, or think about what you need to add to get to 180°.
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180° – 90° – 65° = 25°
OR
90° + 65° = 155°
180° – 155° = 25°

  • What is your answer?
    Check your working.
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The answer is 25°.
You can use the inverse to check that 90° + 65° + 25° = 180°.