Question 231586
 In how many ways can a person enter a room that has three doors and leave it by 
(a) a different door?
# of ways to enter: 3
# of ways to leave:
Total number of choices: 3*2 = 6
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(b) any door?
# of ways to enter: 3
# of ways to leave: 3
Total number of choices: 3*3 = 9
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Cheers,
Stan H.