1990 AHSME Problems/Problem 30
Problem
If where and , and then is an integer. Its units digit is
Solution
but and , so this means that . Since and , all terms are integers and we can continue the recurrence to get the repeating sequence . The number is divisible by three but not by six, so the required element in the sequence is which is answer
See also
1990 AHSME (Problems • Answer Key • Resources) | ||
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