Friday, July 19, 2013

framing of equation

A man buys oranges at the rate of "p" for a $, and by selling them at "q" cents a dozen makes a profit of  "r" %. 

Show that pq -12r = 1200


Answer:
Cost of 12 oranges = 12/p
Selling price of 12 oranges = q/100
Gain = q/100 - 12/p = (pq - 1200)/100p
Gain % = r = 100 [(pq - 1200)/100p] / 12/p
or, 12r = 100p [(pq - 1200)/100p]
or, 12r = pq - 1200
or, pq - 12r = 1200

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