Count the number of ways that each procedure can be done.
Line up 4 people (Mr. Han, Ms. Aguirre, Ms. Torres, and Mr. Birko) for a photograph.
Arrange five books (English, Pre Calculus, Physics, U.S. History, and Korean) on a bookshelf.
How many different answer keys are possible for a 10-question True-False Test?
How many different license plates consist of five symbols, either digits or letters?
Mr. Han gives 20 study questions, from which he will select 8 to be answered on the final exam. How many ways can he select the questions?
The card game “bid Euchre” uses a pack of 24 cards, consisting of ace, king, queen, jack, 10, and 9 in each of the four suits (spades, hearts, diamonds, and clubs). In bid Euchre, a hand consists of 6 cards. Find the probability of each event.
A hand is all spades.
All six cards are from the same suit.
A hand includes all four aces.
There are two precalculus sections at Roosevelt High School. There 12 girls and 8 boys in the 1st period, while there are 10 girls and 15 boys in the 3rd period. If a precalculus student chosen at random happens to be a girl, what is the probability she is from the 1st period?