Difference between revisions of "1965 AHSME Problems/Problem 15"

(made proof more clear and removed inaccurate statement about base 10)
(see also box)
Line 12: Line 12:
  
 
We begin by noting that <math>25_b = 2b+5</math> and <math>52_b = 5b+2</math>. The problem tells us that <math>2*25_b=52_b</math>, so <math>2(2b+5)=5b+2</math>. Solving for b yields the answer <math>\boxed{\textbf{(B) }8}</math>.
 
We begin by noting that <math>25_b = 2b+5</math> and <math>52_b = 5b+2</math>. The problem tells us that <math>2*25_b=52_b</math>, so <math>2(2b+5)=5b+2</math>. Solving for b yields the answer <math>\boxed{\textbf{(B) }8}</math>.
 +
 +
==See Also==
 +
{{AHSME 40p box|year=1965|num-b=14|num-a=16}}
 +
 +
[[Category:Introductory Number Theory Problems]]

Revision as of 13:15, 18 July 2024

Problem

The symbol $25_b$ represents a two-digit number in the base $b$. If the number $52_b$ is double the number $25_b$, then $b$ is:

$\textbf{(A)}\ 7 \qquad  \textbf{(B) }\ 8 \qquad  \textbf{(C) }\ 9 \qquad  \textbf{(D) }\ 11 \qquad  \textbf{(E) }\ 12$

Solution

We begin by noting that $25_b = 2b+5$ and $52_b = 5b+2$. The problem tells us that $2*25_b=52_b$, so $2(2b+5)=5b+2$. Solving for b yields the answer $\boxed{\textbf{(B) }8}$.

See Also

1965 AHSC (ProblemsAnswer KeyResources)
Preceded by
Problem 14
Followed by
Problem 16
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
All AHSME Problems and Solutions