Art of Problem Solving

2002 AMC 12P Problems/Problem 16: Difference between revisions

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== Problem ==
== Problem ==
How many positive [[integer]]s <math>b</math> have the property that <math>\log_{b} 729</math> is a positive integer?
The altitudes of a triangle are <math>12, 15,</math> and <math>20.</math> The largest angle in this triangle is


<math> \mathrm{(A) \ 0 } \qquad \mathrm{(B) \ 1 } \qquad \mathrm{(C) \ 2 } \qquad \mathrm{(D) \ 3 } \qquad \mathrm{(E) \ 4 }  </math>
<math>
\text{(A) }72^\circ
\qquad
\text{(B) }75^\circ
\qquad
\text{(C) }90^\circ
\qquad
\text{(D) }108^\circ
\qquad
\text{(E) }120^\circ
</math>


== Solution ==
== Solution ==

Revision as of 23:51, 29 December 2023

Problem

The altitudes of a triangle are $12, 15,$ and $20.$ The largest angle in this triangle is

$\text{(A) }72^\circ \qquad \text{(B) }75^\circ \qquad \text{(C) }90^\circ \qquad \text{(D) }108^\circ \qquad \text{(E) }120^\circ$

Solution

If $\log_{b} 729 = n$, then $b^n = 729$. Since $729 = 3^6$, $b$ must be $3$ to some factor of 6. Thus, there are four (3, 9, 27, 729) possible values of $b \Longrightarrow \boxed{\mathrm{E}}$.

See also

2002 AMC 12P (ProblemsAnswer KeyResources)
Preceded by
Problem 15
Followed by
Problem 17
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

These problems are copyrighted © by the Mathematical Association of America.