Difference between revisions of "1999 AHSME Problems/Problem 6"

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==Solution==
 
==Solution==
  
<math>2^{1999}\cdot5^{2001}=2^{1999}\cdot5^{1999}\cdot5^{2}=25\cdot10^{1999}</math>, a number with the digits "25" followed by 1999 zeros. The sum of the digits in the decimal form would be <math>2+5=7</math>, thus making the answer <math>\boxed{D}</math>.
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<math>2^{1999}\cdot5^{2001}=2^{1999}\cdot5^{1999}\cdot5^{2}=25\cdot10^{1999}</math>, a number with the digits "25" followed by 1999 zeros. The sum of the digits in the decimal form would be <math>2+5=7</math>, thus making the answer <math>\boxed{\text{D}}</math>.
  
 
== See also ==
 
== See also ==
{{AHSME box|year=1999|before=First question|num-a=2}}
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{{AHSME box|year=1999|num-b=5|num-a=7}}
 
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{{MAA Notice}}
[[Category:Introductory Algebra Problems]]
 

Latest revision as of 22:59, 16 March 2020

Problem

What is the sum of the digits of the decimal form of the product $2^{1999}\cdot 5^{2001}$?

$\textbf{(A)}\ 2\qquad \textbf{(B)}\ 4 \qquad \textbf{(C)}\ 5 \qquad \textbf{(D)}\ 7\qquad \textbf{(E)}\ 10$

Solution

$2^{1999}\cdot5^{2001}=2^{1999}\cdot5^{1999}\cdot5^{2}=25\cdot10^{1999}$, a number with the digits "25" followed by 1999 zeros. The sum of the digits in the decimal form would be $2+5=7$, thus making the answer $\boxed{\text{D}}$.

See also

1999 AHSME (ProblemsAnswer KeyResources)
Preceded by
Problem 5
Followed by
Problem 7
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
All AHSME Problems and Solutions

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