A sporting goods store sells 90 ski jackets at 275 dollars each. Each 15 dollar increase in price results in 5 more jackets being sold. What is the lowest price that would result in revenues of at least $19600?

Question

A sporting goods store sells 90 ski jackets at 275 dollars each. Each 15 dollar increase in price results in 5 more jackets being sold. What is the lowest price that would result in revenues of  at least $19600?

homeworksucks · Answer

So i got the equation of (90+5x)(275-15x)=19600 and expanded

homeworksucks · Answer

I then got -75x^2+25x+5150=0

homeworksucks · Answer

I factored out a 25 and divided both sides by it

homeworksucks · Answer

and got -3x^2+x+206

homeworksucks · Answer

I plugged that into the quadratic formula and got 132.24 jackets and 148.15 dollars..? What?

homeworksucks · Answer

The book's answer is 155 dollars and 130 jackets, where did i go wrong?

homeworksucks · Answer

@shamil98

homeworksucks · Answer

anybody?

homeworksucks · Answer

HelpÉ

anonymous · Answer

Attached is a two solution document prepared with Mathematica 8 Home Edition.