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March 6, 2015

March 6, 2015

Posted by **Diana** on Friday, May 20, 2011 at 8:50am.

Peg spends $7.50 a week for grapefruit. When grapefruit are out of season, she gets 1 fewer grapefruit than when they are in season. If the price decreases by $3 per dozen in season, how many dollars will it cost to buy a dozen grapefruit out of season?

- Help with Math. -
**Reiny**, Friday, May 20, 2011 at 9:08amLet the price per dozen in season be $x

let the price per dozen out of season be $(x+3)

So in season for $7.50 she can buy 7.5/x dozen

or 90/x grapefruits

Out of season for $7.50 she can buy 7.5/(x+3) dozen or 90/(x+3) grapefruits

so 90/x - 90/(x+3) = 1

multiply by x(x+3)

90(x+3) - 90x = x(x+3)

expand and simplify

x^2 + 3x - 270 = 0

(x+18)(x-15) = 0

x = -18 or x = 15 , but clearly x > 0

price out of season was defined as x+3

so out of season they sold at $18 per dozen, WOW!

check:

in season she could buy 7.5/15 = .5 dozen or 6 grapefruits

out of season she could buy 7.5/18 or .4166667 dozen or 5 grapefruits

is 6-5 = 1 ? YES

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