Difference between revisions of "1986 AHSME Problems/Problem 5"

(Created page with "==Problem== Simplify <math>\left(\sqrt[6]{27} - \sqrt{6 \frac{3}{4} }\right)^2</math> <math>\textbf{(A)}\ \frac{3}{4} \qquad \textbf{(B)}\ \frac{\sqrt 3}{2} \qquad \textbf{(C)}...")
 
(Added a solution with explanation)
Line 10: Line 10:
 
    
 
    
 
==Solution==
 
==Solution==
 
+
We have <math>\sqrt[6]{27} = (3^{3})^(\frac{1}{6}) = 3^{\frac{1}{2}} = \sqrt{3}</math> and <math>\sqrt{6 \frac{3}{4}} = \sqrt{\frac{27}{4}} = \frac{3 \sqrt{3}}{2}</math>, so the answer is <math>(\sqrt{3} - \frac{3 \sqrt{3}}{2})^{2} = (-\frac{\sqrt{3}}{2})^{2} = \frac{3}{4}</math>, which is <math>\boxed{A}</math>.
  
 
== See also ==
 
== See also ==

Revision as of 18:09, 1 April 2018

Problem

Simplify $\left(\sqrt[6]{27} - \sqrt{6 \frac{3}{4} }\right)^2$

$\textbf{(A)}\ \frac{3}{4} \qquad \textbf{(B)}\ \frac{\sqrt 3}{2} \qquad \textbf{(C)}\ \frac{3\sqrt 3}{4}\qquad \textbf{(D)}\ \frac{3}{2}\qquad \textbf{(E)}\ \frac{3\sqrt 3}{2}$

Solution

We have $\sqrt[6]{27} = (3^{3})^(\frac{1}{6}) = 3^{\frac{1}{2}} = \sqrt{3}$ and $\sqrt{6 \frac{3}{4}} = \sqrt{\frac{27}{4}} = \frac{3 \sqrt{3}}{2}$, so the answer is $(\sqrt{3} - \frac{3 \sqrt{3}}{2})^{2} = (-\frac{\sqrt{3}}{2})^{2} = \frac{3}{4}$, which is $\boxed{A}$.

See also

1986 AHSME (ProblemsAnswer KeyResources)
Preceded by
Problem 4
Followed by
Problem 6
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 26 27 28 29 30
All AHSME Problems and Solutions

The problems on this page are copyrighted by the Mathematical Association of America's American Mathematics Competitions. AMC logo.png