Difference between revisions of "2007 AMC 12B Problems/Problem 10"
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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? | 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>\mathrm{(A)}\ 4 \qquad \mathrm{(B)}\ 6 \qquad \mathrm{(C)}\ 8 \qquad \mathrm{(D)}\ 10 \qquad \mathrm{(E)}\ 12</math> |
==Solution== | ==Solution== | ||
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Now find the original number of girls: | Now find the original number of girls: | ||
| − | <math> | + | <math>40t/100 = 800/100 = 8</math> |
So, there are 8 girls, <math>\Rightarrow \fbox{C}</math> | So, there are 8 girls, <math>\Rightarrow \fbox{C}</math> | ||
Revision as of 19:40, 25 October 2009
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, 
See Also
| 2007 AMC 12B (Problems • Answer Key • Resources) | |
| Preceded by Problem 9 |
Followed by Problem 11 |
| 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 AMC 12 Problems and Solutions | |
