Geometry and measuresKey Stage 3

Angles on a straight line with algebra

Form and solve an equation using a total of 180°.

  • Add the angle expressions and set the total equal to .
  • Collect like terms, then solve for .

Example 1

Find the value of .

Angles on a straight line add to 180°.Apply this to both sides.Apply this to both sides.
Angles on a straight line add to 180°.
Apply this to both sides.Apply this to both sides.

Example 2

Find the value of .

Angles on a straight line add to 180°.Apply this to both sides.Apply this to both sides.
Angles on a straight line add to 180°.
Apply this to both sides.Apply this to both sides.

Your turn

Question 1

Find the value of .

Check answer
Angles on a straight line add to 180°.Apply this to both sides.Apply this to both sides.
Angles on a straight line add to 180°.
Apply this to both sides.Apply this to both sides.
Question 2

Find the value of .

Check answer
Angles on a straight line add to 180°.Apply this to both sides.Apply this to both sides.
Angles on a straight line add to 180°.
Apply this to both sides.Apply this to both sides.
Question 3

Find the value of .

Check answer
Angles on a straight line add to 180°.Apply this to both sides.Apply this to both sides.
Angles on a straight line add to 180°.
Apply this to both sides.Apply this to both sides.
Question 4

Find the value of .

Check answer
Angles on a straight line add to 180°.Apply this to both sides.Apply this to both sides.
Angles on a straight line add to 180°.
Apply this to both sides.Apply this to both sides.
Question 5

Find the value of .

Check answer
Angles on a straight line add to 180°.Apply this to both sides.Apply this to both sides.
Angles on a straight line add to 180°.
Apply this to both sides.Apply this to both sides.
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