Video Transcript
Evaluate four factorial.
We begin by recalling that the
factorial of any positive integer 𝑛 is the product of all the positive integers
less than or equal to 𝑛. This means that 𝑛 factorial is
equal to 𝑛 multiplied by 𝑛 minus one multiplied by 𝑛 minus two and so on
multiplied by two multiplied by one. Four factorial is therefore equal
to four multiplied by three multiplied by two multiplied by one.
As multiplication is commutative,
we can multiply our integers in any order. For example, four multiplied by
three is equal to 12. Two multiplied by one is equal to
two. And then multiplying 12 by two
gives us an answer of 24. Alternatively, we could multiply
four by three, giving us 12, then multiply this by two, giving us 24, and finally
multiplying 24 by one gives us a final answer of 24. This confirms that four factorial
is equal to 24.
