The World of Algorithms
Class 9 · Mathematics
3 ideas in Class 9 Mathematics, explained in plain words, with games and quizzes to practise.
Addition as an Algorithm
Part of: Addition as an Algorithm
An algorithm is a precise set of steps for solving a task. In addition, align digits by place, add from right to left and carry a new group of ten when needed.
Why it matters. Clear steps make calculations reliable and easier to check.
Try it in two minutes
- Write two numbers vertically with units aligned.
- Add the units and record any carry.
- Continue through each place and include any final carry.
Try at home. Check an addition by estimating the size of the sum.
Divisors and Greatest Common Divisor
Part of: Divisors and Greatest Common Divisor
A divisor divides a number with no remainder. The greatest common divisor is the largest number that divides both given numbers.
Why it matters. This method turns a broad question into a sequence of checks that can be organised and verified.
Try it in two minutes
- List divisors of a small number in order.
- Circle those shared with a second list.
- Choose the largest shared divisor.
Try at home. Use counters or factor pairs to check a proposed divisor.
Lists, Data Structures and Efficiency
Part of: Lists, Data Structures and Efficiency
A data structure organises intermediate values so an algorithm can use them later. The chapter improves a gcd method by reducing repeated scans and keeping only the most recent common divisor.
Why it matters. Efficient organisation can reduce unnecessary work without changing the answer.
Try it in two minutes
- Write a short list in increasing order.
- Mark values shared with a second list.
- Try keeping only the largest shared value found so far.
Try at home. When solving a repeated task, note which information must be saved and which can be discarded.
What your child will practise
- Addition as an Algorithm: Mission Control Quest (Collect the Answer)
- Addition as an Algorithm: Ocean Puzzle (Clue Puzzle)
- Divisors and Greatest Common Divisor: Desert Quest (Flip and Match)
- Divisors and Greatest Common Divisor: Number Quest (Match It Up)
- Lists, Data Structures and Efficiency: Space Quick Fire (Quick Fire)
- Quiz: Addition as an Algorithm (8 questions)
- Quiz: Divisors and Greatest Common Divisor (8 questions)
- Quiz: Lists, Data Structures and Efficiency (8 questions)