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The math department bought some calculators for a total of $240 .
The department head kept one for the math office and then sold the rest for $300 making a profit of $5
on each calculator. How many calculators did the math department buy ?
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Let n be the number of calculators the department bought.
Then it sold (n-1) calculator.
The buying price for each single calculator was .
The selling price was .
The difference in prices was 5 dollars
- = 5 dollars.
Simplify dividing by 5 both sides
- = 1
Multiply both sides by n*(n-1)
60n - 48*(n-1) = n*(n-1)
60n - 48n - 48 = n^2 - n
n^2 - 13n - 48 = 0
(n-16)*(n+3) = 0
Of two roots, 16 and -3, only positive n= 16 is meaningful.
ANSWER. 16 calculators were bought.