Difference between revisions of "2021 WSMO Accuracy Round Problems/Problem 2"
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Note that the numbers on the die are the first 20 triangular numbers. Thus, the expected value of a single roll of this die is <math>\frac{1+3+6+\ldots+210}{20}=\frac{\frac{20\cdot21\cdot22}{6}}{20}=\boxed{77}.</math> | Note that the numbers on the die are the first 20 triangular numbers. Thus, the expected value of a single roll of this die is <math>\frac{1+3+6+\ldots+210}{20}=\frac{\frac{20\cdot21\cdot22}{6}}{20}=\boxed{77}.</math> | ||
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Latest revision as of 12:29, 23 December 2021
Problem
A fair 20-sided die has faces labeled with the numbers 
. Find the expected value of a single roll of this die.
Solution
Note that the numbers on the die are the first 20 triangular numbers. Thus, the expected value of a single roll of this die is 
~pinkpig
