I’m Up and Down, and Round and Round
Class 9 · Mathematics
3 ideas in Class 9 Mathematics, explained in plain words, with games and quizzes to practise.
Circle Basics and Symmetry
Part of: Circle Basics and Symmetry
A circle is the set of plane points at a fixed distance from a centre. A chord joins two points on the circle; a diameter is a chord through the centre.
Why it matters. The centre and radius define a circle precisely.
Try it in two minutes
- Find the fixed centre.
- Measure to the boundary for the radius.
- A chord through the centre is a diameter.
Try at home. Mark a centre and draw several radii and chords.
Chords, Distances and Angles
Part of: Chords, Distances and Angles
Equal chords in a circle are equidistant from the centre, and equal central angles subtend equal chords. An arc subtends twice as large an angle at the centre as at a point on the remaining circle.
Why it matters. These relationships let us reason about a circle without measuring every part.
Try it in two minutes
- Identify the chord or arc.
- Check whether the angle is at the centre or circumference.
- Use equal-chord or double-angle relationships.
Try at home. Draw two chords and compare their distances from the centre.
Concyclic Points and Quadrilaterals
Part of: Concyclic Points and Quadrilaterals
Points on one circle are concyclic. In a cyclic quadrilateral, opposite angles add to 180 degrees. Equal angles subtended by the same segment can establish concyclicity.
Why it matters. Angle sums can show whether four points lie on one circle.
Try it in two minutes
- Check if all four vertices lie on one circle.
- For opposite angles, add their measures.
- A total of 180 degrees fits a cyclic quadrilateral.
Try at home. Draw a quadrilateral inside a circle and measure opposite angles.
What your child will practise
- Chords, Distances and Angles: Jungle Quick Fire (Quick Fire)
- Chords, Distances and Angles: Space Puzzle (Clue Puzzle)
- Circle Basics and Symmetry: Candy Quick Fire (Quick Fire)
- Circle Basics and Symmetry: Mission Control Quest (Match It Up)
- Concyclic Points and Quadrilaterals: Number Quest (Collect the Answer)
- Quiz: Chords, Distances and Angles (8 questions)
- Quiz: Circle Basics and Symmetry (8 questions)
- Quiz: Concyclic Points and Quadrilaterals (8 questions)