Prime Numbers and Prime Factors — Interactive Lesson (Ages 9–14)

☆☆☆☆☆ Add your review • Year 10–11 • 🎓 Interactive Lesson & Activities

A 26-slide interactive lesson on prime numbers and prime factors, using the Sieve of Eratosthenes and factor trees to find highest common factors.

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Which numbers from 1 to 100 are prime? This 26-slide interactive lesson teaches prime numbers and prime factors using the classic Sieve of Eratosthenes method.

Mastering Prime Numbers and Prime Factors

Students review the vocabulary of factors and prime numbers, learning that a prime number has exactly two factors, so 17 is prime because its only factors are 1 and 17, while 1 is not prime because it has only one factor. They follow a step-by-step sieve, crossing out multiples of 2, 3, 5 and 7 from a 1–100 grid to reveal all the prime numbers, then learn that the remaining crossed-out numbers are composite. Students then use this knowledge to write numbers as a product of their factors and use factor trees to find the highest common factor.

What’s Included

26-slide interactive lesson on prime numbers and prime factors
Learning objectives on vocabulary, factors and highest common factor
A step-by-step Sieve of Eratosthenes activity from 1 to 100
Distinguishing prime from composite numbers
Factor-tree questions and instant feedback

Key Benefits for Students

Makes the sieve method for finding primes hands-on
Builds a clear definition of a prime number
Links prime factors to the highest common factor
Instant feedback on answer questions

Why Teachers Love It

No prep — ready for whole-class teaching on an interactive whiteboard
The sieve method gives a memorable, visual method
Self-marking questions support independent practice
Suits teaching, revision and homework
A dependable foundation before HCF and LCM

Love this? You’ll love…

A dependable addition to a number topic, giving students a hands-on way to discover primes for themselves. Confident use of factor trees supports HCF, LCM and simplifying fractions and ratios.

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FAQs

What year group is this for?
Content suits Years 5–9 (ages 9–14); listed under KS4 on this product.

Does it use factor trees?
Yes — to find the highest common factor.

Is it self-marking?
Yes, with instant feedback on the questions.

Year Groups	Year 10–11
Resource Type	🎓 Interactive Lesson & Activities
Format	Digital Only
Curriculum	England & Wales — KS4 (Years 10–11)
Added	11 May 2019