SOLUTION: There is a group of boys and girls standing in line at the bus stop. 15 girls get on the first bus to arrive; now there are 2 boys for each girl still at the bus stop. On the secon

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Question 247114: There is a group of boys and girls standing in line at the bus stop. 15 girls get on the first bus to arrive; now there are 2 boys for each girl still at the bus stop. On the second bus, 45 boys get on; now, at the bus stop, there are 5 girls for each boy. What was the original number of girls ?
(A)40 (B) 43 (C) 29 (D) 50 (E) none of these

Answer by ankor@dixie-net.com(22740) About Me  (Show Source):
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There is a group of boys and girls standing in line at the bus stop.
Let g = no. of girls
Let b = no. of boys
:
15 girls get on the first bus to arrive; now there are 2 boys for each girl still at the bus stop.
b%2F%28g-15%29 = 2
b = 2(g-15)
b = 2g - 30
:
On the second bus, 45 boys get on; now, at the bus stop, there are 5 girls for each boy.
%28b-45%29%2F%28g-15%29 = 1%2F5
cross multiply
5(b-45) = g - 15
5b - 225 = g - 15
5b = g - 15 + 225
5b = g + 210
:
Replace b with (2g-30) from the 1st equation
5(2g - 30) = g + 210
10g - 150 = g + 210
10g - g = 210 + 150
9g = 360
g = 360%2F9
g = 40 girls originally at the bus stop
:
:
To check solution find the no. of boys
b = 2(40) - 30
b = 50 boys
:
%2850+-+45%29%2F%2840-15%29 = 5%2F25 = 1%2F5