Difference between revisions of "2007 AMC 12B Problems/Problem 10"

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==Problem==
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#REDIRECT [[2007 AMC 10B Problems/Problem 14]]
 
 
Some boys and girls are having a car wash to raise money for a class trip to China. Initially <math>40</math>% of the group are girls. Shortly thereafter two girls leave and two boys arrive, and then <math>30</math>% of the group are girls. How many girls were initially in the group?
 
 
 
<math>\mathrm {(A)} 4</math>  <math>\mathrm {(B)} 6</math>  <math>\mathrm {(C)} 8</math>  <math>\mathrm {(D)} 10</math>  <math>\mathrm {(E)} 12</math>
 
 
 
==Solution==
 
 
 
First, determine the total number of people in the group.
 
 
 
<math>2=(40/100-30/100)t</math>
 
 
 
<math>t=200/10=20</math>
 
 
 
Now find the original number of girls:
 
 
 
<math>40/100t = 800/100 = 8</math>
 
 
 
So, there are 8 girls, <math>\Rightarrow \fbox{C}</math>
 

Latest revision as of 16:24, 5 June 2011