The World of Numbers
Class 9 · Mathematics
3 ideas in Class 9 Mathematics, explained in plain words, with games and quizzes to practise.
Integers and Operations
Part of: Integers and Operations
Integers include positive whole numbers, negative whole numbers and zero. They can model fortunes, debts and changes in temperature.
Why it matters. Signs show direction or whether an amount is above or below zero.
Try it in two minutes
- Mark zero as the reference.
- Combine gains and losses with signs.
- Check the sign of products.
Try at home. Represent a small gain or loss on a number line.
Rational and Irrational Numbers
Part of: Rational and Irrational Numbers
A rational number can be written as p divided by q, with integer p and nonzero integer q. Irrational numbers cannot be written as such a ratio.
Why it matters. This distinction explains which numbers have terminating or repeating decimals.
Try it in two minutes
- Look for a fraction representation.
- A nonzero denominator is essential.
- Do not mistake a long decimal for irrationality if it repeats.
Try at home. Sort familiar values into rational and irrational examples.
Decimal Expansions
Part of: Decimal Expansions
A rational number in lowest terms has a terminating decimal when its denominator has only prime factors 2 and 5. Other rational denominators produce repeating decimals. Irrational decimals do not terminate or repeat.
Why it matters. Decimal patterns provide a way to recognise number types.
Try it in two minutes
- Reduce the fraction first.
- Factor its denominator.
- Check for factors other than 2 or 5.
Try at home. Convert simple fractions to decimals and observe whether digits stop or repeat.
What your child will practise
- Decimal Expansions: Desert Puzzle (Clue Puzzle)
- Decimal Expansions: Mission Control Quest (Match It Up)
- Integers and Operations: Jungle Quick Fire (Quick Fire)
- Rational and Irrational Numbers: Number Sort (Sort It Out)
- Rational and Irrational Numbers: Space Quest (Flip and Match)
- Quiz: Decimal Expansions (8 questions)
- Quiz: Integers and Operations (8 questions)
- Quiz: Rational and Irrational Numbers (8 questions)