SOLUTION: Some students planned for a get-together. The budget for food was $500. Five of the students failed to come becuase of the distance, and therefore the cost of food for each member

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Question 132413: Some students planned for a get-together. The budget for food was $500. Five of the students failed to come becuase of the distance, and therefore the cost of food for each member increased by $5. How many students attended the get-together?
Answer by solver91311(24713) About Me  (Show Source):
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In the beginning, there were x students, when five didn't show up, there were x - 5 students.

In the beginning, the cost per student was 500%2Fx but when five students didn't show up, the cost was 500%2F%28x-5%29 and this cost was $5 more than the original cost per student, so:

500%2Fx=500%2F%28x-5%29-5

Need an LCD of x-5 on the right:
500%2Fx=%28500-5%28x-5%29%29%2F%28x-5%29

Simplify the right hand numerator:
500%2Fx=%28525-5x%29%2F%28x-5%29

Cross-multiply:
500%28x-5%29=%28525-5x%29x

Expand:
500x-2500=525x-5x%5E2

Collect terms and put into standard form:
5x%5E2-25x-2500=0

Divide by 5:
x%5E2-5x-500=0

-25%2A20=-500, -25%2B20=-5, so:
%28x-25%29%28x%2B20%29=0

x=25 or x=-20. A negative number for a number of students doesn't make much sense in this context, so exclude -20 as an extraneous root. There were originally 25 students, so 25 - 5 = 20 actually attended.

Check:
500%2F25=20, 500%2F20=25, and 20+%2B+5+=+25