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Difference between revisions of "2004 AMC 12A Problems/Problem 6"

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==Solution==
 
==Solution==
 
<cmath>\begin{eqnarray*}
 
<cmath>\begin{eqnarray*}
−
U-V&=&2004^{2005}\\
+
U-V&=&2004*2004^{2004}\\
−
V-W&=&2004^{2004}\\
+
V-W&=&1*2004^{2004}\\
 
W-X&=&2001*2004^{2004}\\
 
W-X&=&2001*2004^{2004}\\
−
X-Y&=&2004^{2004}\\
+
X-Y&=&1*2004^{2004}\\
 
Y-Z&=&2003*2004^{2003}
 
Y-Z&=&2003*2004^{2003}
 
\end{eqnarray*}</cmath>
 
\end{eqnarray*}</cmath>
  
 
After comparison, <math>U-V</math> is the largest. <math>\mathrm {(A)}</math>
 
After comparison, <math>U-V</math> is the largest. <math>\mathrm {(A)}</math>
 +
 +
 +
==Solution 2==
 +
A quick check reveals the positive integers are in decreasing order. Then note <math>V = 2004^{2005}</math>. <math>\newline</math>
 +
<math>U - V = 2004^{2005} = V</math>, and any of the other differences cannot be greater than or equal to <math>V</math>, hence choose <math>\boxed{A}</math> as the answer.
  
 
==See Also==
 
==See Also==
 
{{AMC12 box|year=2004|ab=A|num-b=5|num-a=7}}
 
{{AMC12 box|year=2004|ab=A|num-b=5|num-a=7}}
 
{{MAA Notice}}
 
{{MAA Notice}}

Latest revision as of 01:10, 30 December 2020

Problem

Let $U=2\cdot 2004^{2005}$, $V=2004^{2005}$, $W=2003\cdot 2004^{2004}$, $X=2\cdot 2004^{2004}$, $Y=2004^{2004}$ and $Z=2004^{2003}$. Which of the following is the largest?

$\mathrm {(A)} U-V \qquad \mathrm {(B)} V-W \qquad \mathrm {(C)} W-X \qquad \mathrm {(D)} X-Y \qquad \mathrm {(E)} Y-Z \qquad$

Solution

\begin{eqnarray*} U-V&=&2004*2004^{2004}\\ V-W&=&1*2004^{2004}\\ W-X&=&2001*2004^{2004}\\ X-Y&=&1*2004^{2004}\\ Y-Z&=&2003*2004^{2003} \end{eqnarray*}

After comparison, $U-V$ is the largest. $\mathrm {(A)}$


Solution 2

A quick check reveals the positive integers are in decreasing order. Then note $V = 2004^{2005}$. $\newline$ $U - V = 2004^{2005} = V$, and any of the other differences cannot be greater than or equal to $V$, hence choose $\boxed{A}$ as the answer.

See Also

2004 AMC 12A (Problems • Answer Key • Resources)
Preceded by
Problem 5 		Followed by
Problem 7
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

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