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Averages Question

by sukhman » Fri Oct 18, 2013 8:03 am
A total of $ 204 was collected from boys and girls of a class of 150 students . If each boy contributes $1 and each girl contributes $1.5 then find the no of boys and girls in the class.
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by mevicks » Fri Oct 18, 2013 8:12 am
Let the number of boys be B and Girls be G
total no of students = 150

B + G = 150 ... (i)

Total contribution = 204
Each boy gives $1 and Each girl gives $1.5

1B + 1.5G = 204 ...(ii)

Subtract (i) from (ii)

0.5 G = 54
[spoiler]G = 108
B = 42[/spoiler]
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by riz_gmat » Fri Oct 18, 2013 8:16 am
Let no: of boys = b , no of girls = g

We get 2 equations,
b(1) + g (1.5) = 204 ---I
b + g = 150 ---II

solving I & II,
we get [spoiler]b = 42 , g = 108[/spoiler]
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by mevicks » Fri Oct 18, 2013 8:23 am
Another way to do this problem is via alligation.

Mean cost = 1.36

Contributions of
B----------G
1---1.36---1.5

B/G = (0.14/0.36) = 7/18

B = 7x
G = 18x
25x = 150
x = 6
[spoiler]B = 42
G = 108[/spoiler]
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