Difference between revisions of "2023 AMC 10A Problems/Problem 5"

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==Solution 1==
 
==Solution 1==
Prime factorization of this gives us <math>2^{15}\cdot3^{5}\cdot5^{15}</math> Pairing <math>2^{15}</math> and <math>5^{15}</math> gives us a number with <math>15</math> zeros, giving us 15 digits. <math>3^5=243</math> and this adds an extra 3 digits. <math>15+3=\text{\boxed{(E)18}}</math>
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Prime factorization of this gives us <math>2^{15}\cdot3^{5}\cdot5^{15}</math>. Pairing <math>2^{15}</math> and <math>5^{15}</math> together gives us a number with <math>15</math> zeros, or 15 digits. <math>3^5=243</math> and this adds an extra 3 digits. <math>15+3=\boxed{\textbf{(E) 18}}</math>
  
 
~zhenghua
 
~zhenghua

Revision as of 20:52, 9 November 2023

Problem

How many digits are in the base-ten representation of $8^5 \cdot 5^{10} \cdot 15^5$?

\[\textbf{(A)}~14\qquad\textbf{(B)}~15\qquad\textbf{(C)}~16\qquad\textbf{(D)}~17\qquad\textbf{(E)}~18\qquad\]

Solution 1

Prime factorization of this gives us $2^{15}\cdot3^{5}\cdot5^{15}$. Pairing $2^{15}$ and $5^{15}$ together gives us a number with $15$ zeros, or 15 digits. $3^5=243$ and this adds an extra 3 digits. $15+3=\boxed{\textbf{(E) 18}}$

~zhenghua

See Also

2023 AMC 12A (ProblemsAnswer KeyResources)
Preceded by
Problem 3
Followed by
Problem 5
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
2023 AMC 10A (ProblemsAnswer KeyResources)
Preceded by
Problem 4
Followed by
Problem 6
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 10 Problems and Solutions

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