Difference between revisions of "2009 AMC 8 Problems/Problem 17"

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==Video Solution==
 
==Video Solution==
 
https://youtu.be/7an5wU9Q5hk?t=2768
 
https://youtu.be/7an5wU9Q5hk?t=2768
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https://www.youtube.com/watch?v=ZuSJdf1zWYw
  
 
==Solution==
 
==Solution==

Revision as of 14:52, 4 July 2022

Problem

The positive integers $x$ and $y$ are the two smallest positive integers for which the product of $360$ and $x$ is a square and the product of $360$ and $y$ is a cube. What is the sum of $x$ and $y$?

$\textbf{(A)}\   80    \qquad \textbf{(B)}\    85   \qquad \textbf{(C)}\    115   \qquad \textbf{(D)}\    165   \qquad \textbf{(E)}\    610$

Video Solution

https://youtu.be/7an5wU9Q5hk?t=2768

https://www.youtube.com/watch?v=ZuSJdf1zWYw

Solution

The prime factorization of $360=2^3 \cdot 3^2 \cdot 5$. If a number is a perfect square, all of the exponents in its prime factorization must be even. Thus we need to multiply by a 2 and a 5, for a product of 10, which is the minimum possible value of x. Similarly, y can be found by making all the exponents divisible by 3, so the minimum possible value of $y$ is $3 \cdot 5^2=75$. Thus, our answer is $x+y=10+75=\boxed{\textbf{(B)}\ 85}$.

See Also

2009 AMC 8 (ProblemsAnswer KeyResources)
Preceded by
Problem 16
Followed by
Problem 18
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 AJHSME/AMC 8 Problems and Solutions

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