How many different ways can 4 paintings be arranged in a row?

For this question, the order of the paintings matter, so we can use generic permutation formula.

P = n!/(n-r)!

where:
n= number of paintings
r = number of paintings we are picking (in this case, we are selecting all paintings, as we are rearranging the paintings)

P = 4!/(4-4)!
P = 24/0! = 24 ways

4 paintings can be arranged in 24 different ways.