Difference between revisions of "2006 Cyprus MO/Lyceum/Problem 10"

 
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==Problem==
 
==Problem==
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If <math>2^x=15</math> and <math>15^y=256</math>, then the product <math>xy</math> equals
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<math>\mathrm{(A)}\ 7\qquad\mathrm{(B)}\ 3\qquad\mathrm{(C)}\ 1\qquad\mathrm{(D)}\ 8\qquad\mathrm{(E)}\ 6</math>
  
 
==Solution==
 
==Solution==
{{solution}}
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<math>(2^x)^y = 2^{xy} = 256</math>, so <math>xy = 8\ \mathrm{(D)}</math>.
  
 
==See also==
 
==See also==
 
{{CYMO box|year=2006|l=Lyceum|num-b=9|num-a=11}}
 
{{CYMO box|year=2006|l=Lyceum|num-b=9|num-a=11}}
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[[Category:Introductory Algebra Problems]]

Latest revision as of 09:37, 27 April 2008

Problem

If $2^x=15$ and $15^y=256$, then the product $xy$ equals

$\mathrm{(A)}\ 7\qquad\mathrm{(B)}\ 3\qquad\mathrm{(C)}\ 1\qquad\mathrm{(D)}\ 8\qquad\mathrm{(E)}\ 6$

Solution

$(2^x)^y = 2^{xy} = 256$, so $xy = 8\ \mathrm{(D)}$.

See also

2006 Cyprus MO, Lyceum (Problems)
Preceded by
Problem 9
Followed by
Problem 11
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