Difference between revisions of "1990 AJHSME Problems/Problem 19"

(Solution)
(Solution)
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<math>p</math> is a person seated, <math>o</math> is an empty seat
 
<math>p</math> is a person seated, <math>o</math> is an empty seat
  
The pattern of seating that results in the fewest occupied seats is opoopoopoo...po
+
The pattern of seating that results in the fewest occupied seats is <math>o<cmath>p</cmath>o<cmath>o</cmath>p<cmath>o</cmath>o<cmath>p</cmath>o</math><math>o</math>...<math>p</math><math>o</math>
 
we can group the seats in 3s
 
we can group the seats in 3s
opo opo opo ...opo
+
<math>o<cmath>p</cmath>o</math> <cmath>o</cmath>p<math></math>o<math> </math>o<cmath>p</cmath>o<math> ...</math>o<cmath>p</cmath>o<math>
  
there are a total of <math>\boxed{B}</math> groups
+
there are a total of </math>\boxed{B}$ groups
  
 
==See Also==
 
==See Also==

Revision as of 07:20, 15 November 2019

Problem

There are $120$ seats in a row. What is the fewest number of seats that must be occupied so the next person to be seated must sit next to someone?

$\text{(A)}\ 30 \qquad \text{(B)}\ 40 \qquad \text{(C)}\ 41 \qquad \text{(D)}\ 60 \qquad \text{(E)}\ 119$

Solution

$p$ is a person seated, $o$ is an empty seat

The pattern of seating that results in the fewest occupied seats is $o<cmath>p</cmath>o<cmath>o</cmath>p<cmath>o</cmath>o<cmath>p</cmath>o$$o$...$p$$o$ we can group the seats in 3s $o<cmath>p</cmath>o$ \[o\]p$$ (Error compiling LaTeX. Unknown error_msg)o$$ (Error compiling LaTeX. Unknown error_msg)o\[p\]o$...$o\[p\]o$there are a total of$\boxed{B}$ groups

See Also

1990 AJHSME (ProblemsAnswer KeyResources)
Preceded by
Problem 18
Followed by
Problem 20
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All AJHSME/AMC 8 Problems and Solutions