Difference between revisions of "1995 AHSME Problems/Problem 15"
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==Solution== | ==Solution== | ||
| − | + | Let us see how the bug moves. | |
| − | + | First, we see that if it starts at point 5, it moves to point 1. | |
| + | |||
| + | At point 1, it moves to point 2. | ||
| + | |||
| + | At point 2, since 2 is even, it moves to point 4. | ||
| + | |||
| + | Then at point 4, it moves to point 1. | ||
| + | |||
| + | We can see that at this point, the bug will cycle between <math>\{{1,2,4}\}%</math> | ||
| + | |||
| + | More specifically, we can see that all numbers congruent to 0 (mod 3) will have the bug on point 2 on that step number. | ||
| + | |||
| + | Thus, we can conclude that the answer is <math>\fbox{\text{(B)}}</math> | ||
==See also== | ==See also== | ||
Revision as of 21:49, 9 February 2012
Problem
Five points on a circle are numbered 1,2,3,4, and 5 in clockwise order. A bug jumps in a clockwise direction from one point to another around the circle; if it is on an odd-numbered point, it moves one point, and if it is on an even-numbered point, it moves two points. If the bug begins on point 5, after 1995 jumps it will be on point
Solution
Let us see how the bug moves.
First, we see that if it starts at point 5, it moves to point 1.
At point 1, it moves to point 2.
At point 2, since 2 is even, it moves to point 4.
Then at point 4, it moves to point 1.
We can see that at this point, the bug will cycle between $\{{1,2,4}\}%$ (Error compiling LaTeX. Unknown error_msg)
More specifically, we can see that all numbers congruent to 0 (mod 3) will have the bug on point 2 on that step number.
Thus, we can conclude that the answer is 
See also
| 1995 AHSME (Problems • Answer Key • Resources) | ||
| Preceded by Problem 14 |
Followed by Problem 16 | |
| 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 • 26 • 27 • 28 • 29 • 30 | ||
| All AHSME Problems and Solutions | ||
