Difference between revisions of "2021 Fall AMC 12B Problems/Problem 23"
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Revision as of 22:44, 23 November 2021
Problem 23
What is the average number of pairs of consecutive integers in a randomly selected subset of distinct integers chosen from the set
? (For example the set
has
pairs of consecutive integers.)
Solution 1
There are possible pairs of consecutive integers, namely
.
The probability that a certain pair of consecutive integers are in the integer subset is
for the first number being chosen, multiplied by
for the second number being chosen.
Therefore, by linearity of expectation, the expected number of pairs of consecutive integers in the 5-integer subset is
~kingofpineapplz
See Also
2021 Fall AMC 12B (Problems • Answer Key • Resources) | |
Preceded by Problem 22 |
Followed by Problem 24 |
1 • 2 • 3 • 4 • 5 • 6 • 7 • 8 • 9 • 10 • 11 • 12 • 13 • 14 • 15 • 16 • 17 • 18 • 19 • 20 • 21 • 22 • 23 • 24 • 25 | |
All AMC 12 Problems and Solutions |
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