Lesson video
In progress...Loading...
Hi, everyone.
I'm Mr. Lund, and in this lesson, we're going to be identifying prime numbers.
Hi, everyone.
Prime numbers have exactly two factors, Which of these numbers are prime? Let me highlight the prime numbers here.
There you go.
The numbers 14 and 26 have four factors each.
The number one only has one factor.
Seven, 11, 17 and two are all prime numbers.
Do you notice number two is the only even prime number? Using the same set of numbers as in the first slide, I'm going to place those numbers into a Venn diagram.
On this side of the Venn diagram, I'm placing some prime numbers.
Those prime numbers are seven, 11 and 17.
On the other side of the diagram, I am placing some even numbers that are not prime.
14 and 26 are even and not prime.
In the intersection of the Venn diagram, I need to put the number two.
Two is a prime number, and an even number.
It is the only even prime number.
Some people think one is a prime number, but it isn't.
So one is an odd number that is not prime.
It has to go here on our Venn diagram.
There's no particular pattern to prime numbers, so you will have to memorise your prime numbers at least up to 20 for GCSE.
If you're studying higher, knowing your prime numbers up to 100 will be sufficient.
Here are some questions for you to try.
Pause the video, and return to check your answers.
Here's the solutions to questions one, two and three.
Don't forget, one is not a prime number.
It only has one factor.
Can you find the six missing primes from this 100 square? Pause the video, and return to check your answers.
Here's the solutions to question four.
How did you do? A bit trickier, this.
Understanding or memorising some of the primes up to 100 can be a tricky task.
Hopefully you got at least the primes up to 20.
Try questions five and six.
Pause the video, and return to check your answers.
Here's the solutions to questions five and six.
How did you do with question six? Three plus 17 equals 20, but also you could have had 13 and seven, both primes that sum to 20.
Here are the solutions for question seven.
Well done for getting this far.
Pause the video, and return to check your answers.
Here's the solutions to question seven.
When you are asked to deal with primes, often you are expected to think about them in relation to other types of numbers.
In this example, we have multiples of three and primes.
