Difference between revisions of "2007 AMC 12B Problems/Problem 10"
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| − | C | + | ==Problem== |
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| + | 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? | ||
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| + | <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> | ||
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| + | ==Solution== | ||
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| + | First, determine the total number of people in the group. | ||
| + | |||
| + | <math>2=10/100t</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> | ||
Revision as of 03:41, 1 September 2008
Problem
Some boys and girls are having a car wash to raise money for a class trip to China. Initially 
% of the group are girls. Shortly thereafter two girls leave and two boys arrive, and then 
% of the group are girls. How many girls were initially in the group?
Solution
First, determine the total number of people in the group.
Now find the original number of girls:
So, there are 8 girls, 
