Difference between revisions of "2024 AMC 10B Problems/Problem 25"

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==Solution 1==
 
==Solution 1==
The <math>3x3x3</math> block has side lengths of <math>3a, 3b, 3c</math>. The <math>2x2x7</math> block has side lengths of <math>2b, 2c, 7a</math>.
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The <math>3</math>x<math>3</math>x<math>3</math> block has side lengths of <math>3a, 3b, 3c</math>. The <math>2</math>x<math>2</math>x<math>7</math> block has side lengths of <math>2b, 2c, 7a</math>.
  
We can create the following system of equations, knowing that the new block has 1 unit taller, deeper, and wider than the original:
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We can create the following system of equations, knowing that the new block has <math>1</math> unit taller, deeper, and wider than the original:
 
<cmath>3a+1 = 2b</cmath>
 
<cmath>3a+1 = 2b</cmath>
 
<cmath>3b+1=2c</cmath>
 
<cmath>3b+1=2c</cmath>

Revision as of 00:28, 14 November 2024

Solution 1

The $3$x$3$x$3$ block has side lengths of $3a, 3b, 3c$. The $2$x$2$x$7$ block has side lengths of $2b, 2c, 7a$.

We can create the following system of equations, knowing that the new block has $1$ unit taller, deeper, and wider than the original: \[3a+1 = 2b\] \[3b+1=2c\] \[3c+1=7a\]

Adding all the equations together, we get $b+c+3 = 4a$. Adding $a-3$ to both sides, we get $a+b+c = 5a-3$. The question states that $a,b,c$ are all relatively prime positive integers. Therefore, our answer must be congruent to $2 \pmod{5}$. The only answer choice satisfying this is $\boxed{92}$. ~lprado