Maths Topic 18 - Angles and lines


Angles and lines: types, intersections, circles, bearings and route diagrams are maths skills that are commonly tested in 11+ and Selective School exams in the UK.

Examples

Example Question 1:

Which two lines are perpendicular to each other?

Answer: A and C

Explanation: Perpendicular lines meet at a right angle (90°).

Example Question 2:

Calculate the angles A, B, C and D.

Answers: A = 70°, B = 35°, C = 60°, D = 60°

Explanation: All the internal angles in any type of triangle add up to 180°

A is in an isosceles triangle with one of the equal angles of 55°. So 55° + 55° = 110° and 180° – 110° = 70°

B is in a scalene triangle. 110° + 35° = 145°. So 180° – 145° = 35°

C is in an equilateral triangle so all the angles are 60°

D is in a right-angled triangle. 90° + 30° = 120°. So 180° – 120° = 60°

Example Question 3:

Calculate angle Χ

Answer: 110°

Explanation: Angle X and the angle of 70° would make a straight line of 180° (co-interior angle). So 180° – 70° = 110°. Or you could spot that angle X is a  corresponding angle the same as the angle of 110°.

Video Tutorials 

Interior Angles in Polygons

 

Estimating Angles

 

Exterior Angles

 

Co-interior Angles

 

Corresponding Angles

 

Alternate Angles

 

Vertically Opposite

 

Straight Line

 

Around a Point

 

Bearings