Difference between revisions of "1971 AHSME Problems/Problem 1"

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== Problem 1 ==
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== Problem ==
 
The number of digits in the number <math>N=2^{12}\times 5^8</math> is
 
The number of digits in the number <math>N=2^{12}\times 5^8</math> is
  
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== Solution ==
 
== Solution ==
<math>N=2^{12}\cdot5^8=2^4\cdot2^8\cdot5^8=2^4\cdot(2\cdot5)^8=2^4\cdot10^8=16\cdot100000000</math>, which has <math>2+8=10</math> digits, so the answer is <math>(\textbf{D})</math>.
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<math>N=2^{12}\cdot5^8=2^4\cdot2^8\cdot5^8=2^4\cdot(2\cdot5)^8=2^4\cdot10^8=16\cdot100000000</math>, which has <math>2+8=10</math> digits, so the answer is <math>\boxed{\textbf{(B) }10}</math>.
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== See Also ==
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{{AHSME 35p box|year=1971|before=First Problem|num-a=2}}
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{{MAA Notice}}
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[[Category:Introductory Number Theory Problems]]

Latest revision as of 08:25, 1 August 2024

Problem

The number of digits in the number $N=2^{12}\times 5^8$ is

$\textbf{(A) }9\qquad \textbf{(B) }10\qquad \textbf{(C) }11\qquad \textbf{(D) }12\qquad  \textbf{(E) }20$

Solution

$N=2^{12}\cdot5^8=2^4\cdot2^8\cdot5^8=2^4\cdot(2\cdot5)^8=2^4\cdot10^8=16\cdot100000000$, which has $2+8=10$ digits, so the answer is $\boxed{\textbf{(B) }10}$.

See Also

1971 AHSC (ProblemsAnswer KeyResources)
Preceded by
First Problem
Followed by
Problem 2
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
All AHSME Problems and Solutions

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