In how many ways you can put 20 books on 50 shelves so that there is not more than one book on a shelf?

9514 1404 393

Step-by-step explanation:

If order doesn't matter, the number is the combinations of 50 things taken 20 at a time:

  50C20 = 47129212243960 ≈ 4.713×10^13

If order does matter, then the number of ways is this value multiplied by 20!:

  50P20 = 114660755112113373922453094400000 ≈ 1.147×10^32

nCk = n!/(k!(n-k)!)

nPk = n!/(n-k)!

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.

6/20

step-by-step explanation: