Test: Probability I - Ambitious

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Question 1:   How many four-digit numbers can you get out of 0, 3, 7, 8 ?
9
18
30
24
Question 2:   There are 19 balls in the box: 10 of red ones and 9 of blue ones. In how many ways can two balls of the same color be picked?
162
171
9
81
Question 3:   In how many ways can you pick a captain and his deputy in a group of 23 soldiers?
506
2 23 ×100%
253
2 23!
Question 4:   John has 4 cats. In how many ways he can take 2 of them in his hands (one - in left hand, another - in right)?
8
24
12
2
Question 5:   Three passengers walk into the elevator of the 11 -floor building (ground floor is not included). In how many ways all three passengers can get out on different floors?
33
165
495
990
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