Video Transcript
What is the greatest prime number
between 15 and 24?
Let’s start by identifying which
numbers are prime between 15 and 24. Or better yet, let’s start by
eliminating numbers we know are not prime. Any number on this number line
that’s even is not a prime number because it’s divisible by two. So we can eliminate 16, 18, 20, 22,
and 24.
I also know that 15 is divisible by
three, which means 15 can’t be a prime number. 21 is divisible by three. 17 has no other factors; it’s only
divisible by one and itself. It’s a prime number. 19 has no other factors; it’s only
divisible by one and itself. It is a prime number. The same thing is true for 23. 23 is not divisible by anything
except for one and itself.
On our number line, we’ve
identified three prime numbers: 17, 19, and 23. Our question is asking what is the
greatest prime number between 15 and 24.
The greatest prime number between
15 and 24 is 23.
