A building has 20 floors above the ground floor. Four people walk into this building on the ground floor, on their way to some floor above the ground.

When they reach the elevator, each person only presses the button of the floor they are going to.

What is the probability that 4 buttons for consecutive floors are pressed?

1/24

Step-by-step explanation:

using Permutations and Combinations

step-by-step explanation:

3024 rhe base is what up in worry about

a) one student is chosen from classroom a, then a student is chosen from classroom b.  

step-by-step explanation:

independent events are ones in which the probability of one event does not affect the probability of the second event.

one student is chosen from classroom a; this does not affect the chances of choosing a student from classroom b.   this makes these independent events.

when one card is chosen from a standard deck and then set aside before a second card is chosen, the probability of the second card being chosen changes.   this makes them dependent events.

when one student is chosen from classroom a and then a second student is chosen from classroom a, the probability of choosing the second student changes.   this makes them dependent events.

when a letter is chosen from the alphabet and then a second letter is chosen, the probability of choosing the second letter changes.   this makes them dependent events.