Prime Time
Class 6 · Mathematics
4 ideas in Class 6 Mathematics, explained in plain words, with games and quizzes to practise.
Understanding Multiples and Common Multiples
Part of: Multiples and Factors
A multiple of a number is what you get when you multiply that number by whole numbers. For example, multiples of 4 are 4, 8, 12, 16, 20. When two or more numbers share some multiples, those shared multiples are called common multiples. The multiples of 3 are 3, 6, 9, 12, 15, 18, 21, 24 and the multiples of 4 are 4, 8, 12, 16, 20, 24. Notice that 12 and 24 appear in both lists—these are common multiples of 3 and 4.
Why it matters. Multiples help us understand patterns and solve real problems. When arranging chairs in equal rows, planning bell schedules at school, or finding when two buses arrive at the same time, we use common multiples. The smallest common multiple of two numbers is especially useful because it tells us when events sync up most quickly.
Try it in two minutes
- Count by 2s: 2, 4, 6, 8, 10, 12. Ask: can you say these numbers out loud while jumping?
- Now count by 3s: 3, 6, 9, 12, 15. Do this as well.
- Ask your child: which numbers appeared in both lists? Those are common multiples.
Try at home. Bounce a ball every 4 seconds and ring a bell every 6 seconds. Notice at which times you do both actions at once—these happen at common multiples of 4 and 6.
Factors and Common Factors
Part of: Multiples and Factors
A factor of a number divides that number evenly with no remainder. The factors of 12 are 1, 2, 3, 4, 6, and 12 because each divides 12 without a remainder. Two numbers can share some factors, called common factors. For example, the factors of 12 are 1, 2, 3, 4, 6, 12 and the factors of 18 are 1, 2, 3, 6, 9, 18. Notice that 1, 2, 3, and 6 appear in both lists—these are the common factors.
Why it matters. Understanding factors helps us divide groups fairly, cut materials into equal pieces, and simplify fractions. When a teacher wants to divide 20 students into equal groups, knowing the factors of 20 tells us that groups of 1, 2, 4, 5, 10, or 20 are all possible.
Try it in two minutes
- Give your child 12 small objects like buttons or coins.
- Ask: how many different ways can you arrange them in equal rows? Try 1 row of 12, 2 rows of 6, 3 rows of 4, 4 rows of 3, 6 rows of 2, 12 rows of 1.
- Say: the row sizes are all the factors of 12.
Try at home. Ask your child to find all the ways to arrange 24 pencils in equal rows on a shelf. Each row size is a factor of 24.
Prime and Composite Numbers
Part of: Primes and Factorisation
A prime number has exactly two factors: 1 and the number itself. Examples are 2, 3, 5, 7, 11, 13. A composite number has more than two factors. For example, 8 has factors 1, 2, 4, 8, so it is composite. The number 1 is special—it is neither prime nor composite because it has only one factor.
Why it matters. Prime numbers are the building blocks of all whole numbers. Many important discoveries in mathematics and computer science depend on understanding primes. They also appear in secret codes used by banks and the internet to keep information safe.
Try it in two minutes
- Write numbers from 1 to 20 on paper.
- Cross out 1. Circle 2 and cross out all multiples of 2.
- Circle 3 and cross out all multiples of 3. The circled numbers are primes.
Try at home. Collect 13 small objects. Try arranging them in a rectangular pattern with rows and columns. You can only make 1 row of 13 or 13 rows of 1 because 13 is prime. Try the same with 12 objects and see how many different rectangular arrangements are possible.
Prime Factorisation and Co-primes
Part of: Primes and Factorisation
Every whole number greater than 1 can be written as a product of prime numbers. This is called prime factorisation. For example, 12 = 2 × 2 × 3, and 30 = 2 × 3 × 5. Two numbers are co-prime if they share no common factors except 1. For example, 8 = 2 × 2 × 2 and 9 = 3 × 3 have no prime factors in common, so they are co-prime.
Why it matters. Prime factorisation helps us understand the structure of numbers and simplify fractions. Co-prime numbers appear in lock-and-key patterns called co-prime art, and they are essential for secret codes used in computers and security.
Try it in two minutes
- Take the number 20. Can you write it as a product of smaller numbers? Try 20 = 4 × 5.
- Now break 4 further: 4 = 2 × 2. So 20 = 2 × 2 × 5, all primes.
- Try with 18: 18 = 2 × 9 = 2 × 3 × 3.
Try at home. Pick any number between 10 and 30. Write it as a product of primes by repeatedly dividing by small primes like 2, 3, 5.
What your child will practise
- Factors and Common Factors: Candy Puzzle (Clue Puzzle)
- Factors and Common Factors: Space Quest (Flip and Match)
- Prime and Composite Numbers: Ocean Sort (Sort It Out)
- Prime Factorisation and Co-primes: Candy Quick Fire (Quick Fire)
- Understanding Multiples and Common Multiples: Ocean Quest (Collect the Answer)
- Quiz: Factors and Common Factors (8 questions)
- Quiz: Prime Factorisation and Co-primes (8 questions)
- Quiz: Prime and Composite Numbers (8 questions)
- Quiz: Understanding Multiples and Common Multiples (8 questions)