Checking and securing understanding of prime factorisation | Maths

Starter quiz

Calculate 0.25 × 0.94, giving your answer as a decimal.

'0.235' ✓
Which of these is equivalent to 0.8?

$\frac{8}{100}$

$\frac{4}{5}$ ✓

$\frac{2}{10}$
Calculate 3.25 × 7.94, giving your answer as a decimal.

'25.805' ✓
Calculate -0.3 + 9.1, giving your answer as a decimal.

'8.8' ✓
Calculate 0.28 ÷ 0.04, giving your answer as a decimal.

'7' ✓
Convert 3.4 into a mixed number.

$\frac{34}{10}$

$3\frac{2}{5}$ ✓

$\frac{34}{100}$

Exit quiz

What number is written as $2 × 5^2 × 19$ as a product of its prime factors?

'950' ✓
What number is written as $2 × 5 × 31$ as a product of its prime factors?

'310' ✓
What number is written as $3 × 5 × 11$ as a product of its prime factors?

'165' ✓
Which of these is a prime factor of 10905?

2

5 ✓

8
Which of these is the prime factorisation of 450?

$2 × 3 × 5$

$2 × 3^2 × 5$

$2 × 3 ^2× 5^2$ ✓
Which of these is the prime factorisation of 539?

$7^2 × 11$ ✓

$2^3 × 7^2$

$3^3 × 7^2$

Worksheet

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Lesson Details

Key learning points

Every positive integer can be broken down into prime factors.
Every positive integer can be written as a product of its prime factors.
Prime factor products can be simplified by using index notation.

Common misconception

Use of addition instead of multiplication when the decomposing the number.

Reiterate that the product of prime factors is unique. This should also be helped when setting the decomposition out as products rather than just a 'tree'.

Keywords

Product of primes - Expressing a number as a product of primes means writing it uniquely as a product of its factors that are prime numbers.
Prime factors - Prime factors are the factors of a number that are, themselves, prime.
Prime factorisation - Prime factorisation is a method to find the prime factors of a given integer.