suppose we want to choose three objects, without replacement from the four objects pencil, eraser, desk, and chair.
a) how many ways can this be done, if the order of the choices matters?
b) how many ways can this be done, if the order of the choices does not matter?
Part a)
Find out the permutation
Applying the formula
P=n!/[n-r]!
where
n=4
r=3
substitute
P=4!/[4-3]!
P=24
answer part a is 24 ways
Part b
Find out the combination
Applying the formula
C=n!/[(n-r)!*r!]
where
n=4
r=3
substitute
C=4!/[(4-3)!*3!]
C=4
answer part b is 4 ways
