1988 AHSME Problems/Problem 12
Revision as of 17:14, 26 February 2018 by Hapaxoromenon (talk | contribs) (Added a solution with explanation)
Problem
Each integer through is written on a separate slip of paper and all nine slips are put into a hat. Jack picks one of these slips at random and puts it back. Then Jill picks a slip at random. Which digit is most likely to be the units digit of the sum of Jack's integer and Jill's integer?
Solution
We can draw a sample space diagram, and find that of the possibilities, of them give a sum of , and each other sum mod (from to ) is given by of the possibilities (and indeed we can check that ). Thus is the most likely, so the answer is .
See also
1988 AHSME (Problems • Answer Key • Resources) | ||
Preceded by Problem 11 |
Followed by Problem 13 | |
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All AHSME Problems and Solutions |
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