A health inspector must visit 4 of restaurants on Monday. In how many can she pick a first, second, third, and fourth restaurant visit?
Solution:-
The number of ways the inspector can pick the first restaurant is 10.
The number of ways the inspector can pick the second restaurant is 9.
Continuing in this manner, you can see that this a permutation of 10 things taken 4 at a time.
P(10,4) = 
She can visit the restaurants in 5040 ways.