Combination Problem (pre-cal) part 2?

Question

The teacher has a row of 5 desks in her classroom. How many ways can she arrange the 5 students in a row in those desks? Answer: 120

but why 120? i thought it would be 25? I seriously don't know what im doing for these problems, whoever helped me last 5 mins ago ! it helped so much !

Answer 1

The 120 is calculated: 5 * 4 * 3 * 2 * 1 and gives the total number of possible arrangements.

EDIT:

It's actually a factorial. This particular example is known as "five factorial" and is denoted by 5!

n! is said to be defined as:

n! = (n)*(n-1)*(n-2)*...*(1), where n is a positive integer and 0! is defined as 1

If you had a row of 10, it would be 10 * 9 * 8...*1