1950 AHSME Problems/Problem 26: Difference between revisions
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<math> \textbf{(A)}\ \frac{b}{n}\qquad\textbf{(B)}\ bn\qquad\textbf{(C)}\ 10^{b}n\qquad\textbf{(D)}\ b-10^{n}\qquad\textbf{(E)}\ \frac{10^{b}}{n} </math> | <math> \textbf{(A)}\ \frac{b}{n}\qquad\textbf{(B)}\ bn\qquad\textbf{(C)}\ 10^{b}n\qquad\textbf{(D)}\ b-10^{n}\qquad\textbf{(E)}\ \frac{10^{b}}{n} </math> | ||
==Solution== | ==Solution 1== | ||
We have <math>b=\log_{10}{10^b}</math>. Substituting, we find <math>\log_{10}{m}= \log_{10}{10^b}-\log_{10}{n}</math>. Using <math>\log{a}-\log{b}=\log{\dfrac{a}{b}}</math>, the left side becomes <math>\log_{10}{\dfrac{10^b}{n}}</math>. Because <math>\log_{10}{m}=\log_{10}{\dfrac{10^b}{n}}</math>, <math>m=\boxed{\mathrm{(E) }\dfrac{10^b}{n}}</math>. | We have <math>b=\log_{10}{10^b}</math>. Substituting, we find <math>\log_{10}{m}= \log_{10}{10^b}-\log_{10}{n}</math>. Using <math>\log{a}-\log{b}=\log{\dfrac{a}{b}}</math>, the left side becomes <math>\log_{10}{\dfrac{10^b}{n}}</math>. Because <math>\log_{10}{m}=\log_{10}{\dfrac{10^b}{n}}</math>, <math>m=\boxed{\mathrm{(E) }\dfrac{10^b}{n}}</math>. | ||
==Solution 2== | |||
adding <math>\log_{10} n</math> to both sides: | |||
<cmath>\log_{10} m + \log_{10} n=b</cmath> | |||
using the logarithm property <cmath>\log_a {b} + \log_a {c}=\log_a{bc}</cmath>: | |||
<cmath>\log_{10} {mn}=b</cmath> | |||
rewriting in exponential notation: | |||
<cmath>10^b=mn</cmath> | |||
<cmath>m=\boxed{\mathrm{(E) }\dfrac{10^b}{n}}</cmath> | |||
==See Also== | ==See Also== | ||
Revision as of 00:22, 10 June 2020
Problem
If 
, then 
Solution 1
We have 
. Substituting, we find 
. Using 
, the left side becomes 
. Because 
, 
.
Solution 2
adding 
to both sides:
![\[\log_{10} m + \log_{10} n=b\]](http://latex.artofproblemsolving.com/a/c/d/acd4aae819e142a2d1f955adf4173b699ab685c3.png)
using the logarithm property ![\[\log_a {b} + \log_a {c}=\log_a{bc}\]](http://latex.artofproblemsolving.com/f/7/d/f7d8784305ed4233756fa921827611db634bfe3b.png)
:
![\[\log_{10} {mn}=b\]](http://latex.artofproblemsolving.com/c/b/d/cbded8a2340f38f2e9c93e2c89067f6457b1429b.png)
rewriting in exponential notation:
![\[10^b=mn\]](http://latex.artofproblemsolving.com/8/b/1/8b10c86f05dc25ebc5f3cea860f97588d503106d.png)
![\[m=\boxed{\mathrm{(E) }\dfrac{10^b}{n}}\]](http://latex.artofproblemsolving.com/9/9/d/99d0c6f5d34ea6d45d7ce6820dc2985563f111a6.png)
See Also
| 1950 AHSC (Problems • Answer Key • Resources) | ||
| Preceded by Problem 25 |
Followed by Problem 27 | |
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| All AHSME Problems and Solutions | ||
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