What is factorial?

A factorial is like when you count how many ways you can line up your toys.

Imagine you have 4 favorite toys: a teddy bear, a robot, a dinosaur, and a ball. You want to know how many different orders you can arrange them in. That’s what a factorial does, it tells you the number of ways things can be arranged when you use all of them.

The word factorial is written with an exclamation mark: !. So, 4! means 4 factorial, and it equals 4 × 3 × 2 × 1 = 24. That’s how many different ways you can line up your four toys.

If you only had two toys, like a robot and a ball, the number of ways to arrange them would be 2! = 2 × 1 = 2: robot first or ball first, simple!

Each time you add another toy, you multiply by one more number. So if you have five toys, it’s 5 × 4 × 3 × 2 × 1 = 120 ways to line them up.

Factorials are like a fun game that grows bigger every time you play with more toys, and they help grown-ups solve tricky problems too!