Difference between revisions of "2017 AMC 8 Problems/Problem 15"
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<math>\textbf{(A) }8\qquad\textbf{(B) }9\qquad\textbf{(C) }12\qquad\textbf{(D) }24\qquad\textbf{(E) }36</math> | <math>\textbf{(A) }8\qquad\textbf{(B) }9\qquad\textbf{(C) }12\qquad\textbf{(D) }24\qquad\textbf{(E) }36</math> | ||
| − | ==Solution 1== | + | ==Solution 1 (Not Very Good)== |
Notice that the upper-most section contains a 3 by 3 square that looks like: | Notice that the upper-most section contains a 3 by 3 square that looks like: | ||
Revision as of 07:53, 10 January 2022
Contents
Problem
In the arrangement of letters and numerals below, by how many different paths can one spell AMC8? Beginning at the A in the middle, a path only allows moves from one letter to an adjacent (above, below, left, or right, but not diagonal) letter. One example of such a path is traced in the picture.
![[asy] fill((0.5, 4.5)--(1.5,4.5)--(1.5,2.5)--(0.5,2.5)--cycle,lightgray); fill((1.5,3.5)--(2.5,3.5)--(2.5,1.5)--(1.5,1.5)--cycle,lightgray); label("$8$", (1, 0)); label("$C$", (2, 0)); label("$8$", (3, 0)); label("$8$", (0, 1)); label("$C$", (1, 1)); label("$M$", (2, 1)); label("$C$", (3, 1)); label("$8$", (4, 1)); label("$C$", (0, 2)); label("$M$", (1, 2)); label("$A$", (2, 2)); label("$M$", (3, 2)); label("$C$", (4, 2)); label("$8$", (0, 3)); label("$C$", (1, 3)); label("$M$", (2, 3)); label("$C$", (3, 3)); label("$8$", (4, 3)); label("$8$", (1, 4)); label("$C$", (2, 4)); label("$8$", (3, 4));[/asy]](http://latex.artofproblemsolving.com/c/3/b/c3b81f82e730c8fce3fba2c0d1e893252c432d58.png)
Solution 1 (Not Very Good)
Notice that the upper-most section contains a 3 by 3 square that looks like:
![[asy]label("$8$", (1, 2)); label("$C$", (2, 2)); label("$8$", (3, 2)); label("$C$", (1, 1)); label("$M$", (2, 1)); label("$C$", (3, 1)); label("$M$", (1, 0)); label("$A$", (2, 0)); label("$M$", (3, 0));[/asy]](http://latex.artofproblemsolving.com/4/e/7/4e757a2a293bbc0f2888163537a04662facfe134.png)
It has 6 paths in which you can spell out AMC8. You will find four identical copies of this square in the figure, so multiply 
to get 
total paths.
Solution 2
There are three different kinds of paths that are on this diagram. The first kind is when you directly count 
, 
, 
in a straight line. The second is when you count , turn left or right to get , then go up or down to count 
and . The third is the one where you start with , move up or down to count , turn left or right to count , then move straight again to get .
There are 8 paths for each kind of path, making for 
paths.
Solution 3
Notice that the is adjacent to 
s, each is adjacent to 
s, and each is adjacent to 
's. Thus, the answer is 
Video Solution
See Also
| 2017 AMC 8 (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 | ||
| All AJHSME/AMC 8 Problems and Solutions | ||
The problems on this page are copyrighted by the Mathematical Association of America's American Mathematics Competitions. 
