Difference between revisions of "2003 AMC 12B Problems/Problem 1"

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{{duplicate|[[2003 AMC 12B Problems|2003 AMC 12B #1]] and [[2003 AMC 10B Problems|2003 AMC 10B #1]]}}
 
{{duplicate|[[2003 AMC 12B Problems|2003 AMC 12B #1]] and [[2003 AMC 10B Problems|2003 AMC 10B #1]]}}
  
==Problem==
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== Problem ==
 +
 
 
Which of the following is the same as
 
Which of the following is the same as
  
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</math>
 
</math>
  
==Solution==
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== Solution 1 ==
  
The numbers in the numerator and denominator can be grouped like this:
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<cmath>\frac{2-4+6-8+10-12+14}{3-6+9-12+15-18+21}=\frac{2+(-4+6)+(-8+10)+(-12+14)}{3+(-6+9)+(-12+15)+(-18+21)}=\frac{2\cdot4}{3\cdot4}=\text {(C) } \frac{2}{3}</cmath>
  
<cmath>
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== Solution 2 ==
\begin{align*}
 
2+(-4+6)+(-8+10)+(-12+14)&=2*4\\
 
3+(-6+9)+(-12+15)+(-18+21)&=3*4\\
 
\frac{2*4}{3*4}&=\frac{2}{3} \Rightarrow \text {(C)}
 
\end{align*}</cmath>
 
  
Alternatively, notice that each term in the numerator is <math>\frac{2}{3}</math> of a term in the denominator, so the quotient has to be <math>\frac{2}{3}</math>.
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Each term in the numerator is <math>\text {(C) } \frac{2}{3}</math> of a corresponding term in the denominator, so this must be the quotient.
  
==See also==
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== See also ==
 
{{AMC12 box|year=2003|ab=B|before=First Question|num-a=2}}
 
{{AMC12 box|year=2003|ab=B|before=First Question|num-a=2}}
 
{{AMC10 box|year=2003|ab=B|before=First Question|num-a=2}}
 
{{AMC10 box|year=2003|ab=B|before=First Question|num-a=2}}
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{{MAA Notice}}
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[[Category:Introductory Algebra Problems]]
 
[[Category:Introductory Algebra Problems]]
{{MAA Notice}}
 

Latest revision as of 21:43, 16 January 2025

The following problem is from both the 2003 AMC 12B #1 and 2003 AMC 10B #1, so both problems redirect to this page.

Problem

Which of the following is the same as

\[\frac{2-4+6-8+10-12+14}{3-6+9-12+15-18+21}?\]

$\text {(A) } -1 \qquad \text {(B) } -\frac{2}{3} \qquad \text {(C) } \frac{2}{3} \qquad \text {(D) } 1 \qquad \text {(E) } \frac{14}{3}$

Solution 1

\[\frac{2-4+6-8+10-12+14}{3-6+9-12+15-18+21}=\frac{2+(-4+6)+(-8+10)+(-12+14)}{3+(-6+9)+(-12+15)+(-18+21)}=\frac{2\cdot4}{3\cdot4}=\text {(C) } \frac{2}{3}\]

Solution 2

Each term in the numerator is $\text {(C) } \frac{2}{3}$ of a corresponding term in the denominator, so this must be the quotient.

See also

2003 AMC 12B (ProblemsAnswer KeyResources)
Preceded by
First Question
Followed by
Problem 2
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 12 Problems and Solutions
2003 AMC 10B (ProblemsAnswer KeyResources)
Preceded by
First Question
Followed by
Problem 2
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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