2009 AMC 8 Problems/Problem 21: Difference between revisions
Mrdavid445 (talk | contribs) Created page with "==Problem== Andy and Bethany have a rectangular array of numbers with <math> 40</math> rows and <math> 75</math> columns. Andy adds the numbers in each row. The average of his <..." |
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\textbf{(D)}\ \frac{15}{8} \qquad | \textbf{(D)}\ \frac{15}{8} \qquad | ||
\textbf{(E)}\ \frac{225}{64}</math> | \textbf{(E)}\ \frac{225}{64}</math> | ||
==Solution== | |||
First, note that <math>40A=75B=\text{sum of the numbers in the array}</math>. Solving for <math> \frac{A}{B}</math>, we get <math> \frac{75}{40} =\frac{15}{8} =\frac{A}{B}</math>. <math> \boxed{\text{D}}</math>. | |||
Revision as of 08:31, 27 April 2012
Problem
Andy and Bethany have a rectangular array of numbers with 
rows and 
columns. Andy adds the numbers in each row. The average of his sums is 
. Bethany adds the numbers in each column. The average of her sums is 
. What is the value of 
?
Solution
First, note that 
. Solving for , we get 
. 
.
