2020 AMC 10A Problems/Problem 22
For how many positive integers isnot divisible by ? (Recall that is the greatest integer less than or equal to .)
Solution
Let . If the expression is not divisible by , then the three terms in the expression must be , which would imply that is divisible by but not , or , which would imply that is divisible by but not . has factors, and has factors. However, does not work because is divisible by both and , and since is counted twice, the answer is .
See Also
2020 AMC 10A (Problems • Answer Key • Resources) | ||
Preceded by Problem 21 |
Followed by Problem 23 | |
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 10 Problems and Solutions |
The problems on this page are copyrighted by the Mathematical Association of America's American Mathematics Competitions.