Difference between revisions of "2019 AMC 10A Problems/Problem 10"

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==Solution==
 
==Solution==
Because this is a <math>10</math> by <math>17</math> grid, the number of tiles that the bug visits is <math>10+17-1=\boxed{26\implies (C)}</math>.  
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The number of tiles the bug visits is equal to <math>1</math> plus the number of times it crosses a horizontal or vertical line.  As it must cross <math>16</math> horizontal lines and <math>9</math> vertical lines, it must be that the bug visits a total of <math>16+9+1 = \boxed{\textbf{(C) }26}</math> squares.
  
Note: You will find that the general formula for this is <math>a+b-lcm(a,b)</math>
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Note: The general formula for this is <math>a+b-\gcd(a,b)</math>
  
 
==See Also==
 
==See Also==

Revision as of 18:55, 9 February 2019

Problem

A rectangular floor that is $10$ feet wide and $17$ feet long is tiled with $170$ one-foot square tiles. A bug walks from one corner to the opposite corner in a straight line. Including the first and the last tile, how many tiles does the bug visit?

$\textbf{(A) } 17 \qquad\textbf{(B) } 25 \qquad\textbf{(C) } 26 \qquad\textbf{(D) } 27 \qquad\textbf{(E) } 28$

Solution

The number of tiles the bug visits is equal to $1$ plus the number of times it crosses a horizontal or vertical line. As it must cross $16$ horizontal lines and $9$ vertical lines, it must be that the bug visits a total of $16+9+1 = \boxed{\textbf{(C) }26}$ squares.

Note: The general formula for this is $a+b-\gcd(a,b)$

See Also

2019 AMC 10A (ProblemsAnswer KeyResources)
Preceded by
Problem 9
Followed by
Problem 11
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

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