Difference between revisions of "1955 AHSME Problems/Problem 42"

(Created the page, not sure how to create LaTeX solution.)
 
(Solution)
 
(3 intermediate revisions by 2 users not shown)
Line 5: Line 5:
  
  
== Solution ==
+
== Solution ==  
 +
Here, we are told that the two quantities are equal.
  
 +
Squaring both sides, we get: <math>a+\frac{b}{c}=a^2*\frac{b}{c}</math>.
 +
 +
Multiply both sides by <math>c</math>: <math>ac+b=ba^2</math>.
 +
 +
Looking at all answer choices, we can see that <math>ac=ba^2-b=b(a^2-1)</math>.
 +
 +
This means that <math>c=\frac{b(a^2-1)}{a}</math>, and this is option C. Therefore chose <math>\boxed{C}</math> as your answer.
 +
 +
~hastapasta
  
 
== See Also ==
 
== See Also ==

Latest revision as of 17:38, 18 February 2022

Problem

If $a, b$, and $c$ are positive integers, the radicals $\sqrt{a+\frac{b}{c}}$ and $a\sqrt{\frac{b}{c}}$ are equal when and only when:

$\textbf{(A)}\ a=b=c=1\qquad\textbf{(B)}\ a=b\text{ and }c=a=1\qquad\textbf{(C)}\ c=\frac{b(a^2-1)}{a}\\ \textbf{(D)}\ a=b\text{ and }c\text{ is any value}\qquad\textbf{(E)}\ a=b\text{ and }c=a-1$


Solution

Here, we are told that the two quantities are equal.

Squaring both sides, we get: $a+\frac{b}{c}=a^2*\frac{b}{c}$.

Multiply both sides by $c$: $ac+b=ba^2$.

Looking at all answer choices, we can see that $ac=ba^2-b=b(a^2-1)$.

This means that $c=\frac{b(a^2-1)}{a}$, and this is option C. Therefore chose $\boxed{C}$ as your answer.

~hastapasta

See Also

1955 AHSC (ProblemsAnswer KeyResources)
Preceded by
Problem 41
Followed by
Problem 43
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 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50
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