SOLUTION: A 7-INCH BY 10-INCH RECTANGLE HAS A STRIP OF UNIFORM WIDTH, X INCHES, AROUND ITS OUTSIDE. IF THE AREA OF THE STRIP IF 50 SQUARE INCHES, WHAT IS THE WIDTH OF THE STRIP?

Algebra ->  Quadratic Equations and Parabolas  -> Quadratic Equations Lessons  -> Quadratic Equation Lesson -> SOLUTION: A 7-INCH BY 10-INCH RECTANGLE HAS A STRIP OF UNIFORM WIDTH, X INCHES, AROUND ITS OUTSIDE. IF THE AREA OF THE STRIP IF 50 SQUARE INCHES, WHAT IS THE WIDTH OF THE STRIP?      Log On


   

Question 179279: A 7-INCH BY 10-INCH RECTANGLE HAS A STRIP OF UNIFORM WIDTH, X INCHES, AROUND ITS OUTSIDE. IF THE AREA OF THE STRIP IF 50 SQUARE INCHES, WHAT IS THE WIDTH OF THE STRIP?
Answer by checkley75(3666) About Me  (Show Source):
You can put this solution on YOUR website!
7*10=70 in^2
(7+2x)(10+2x)=70+50
70+20x+14x+4x^2=120
4x^2+34x+70-120=0
4x^2+34x-50=0
Using the quadratic equation x+=+%28-b+%2B-+sqrt%28+b%5E2-4%2Aa%2Ac+%29%29%2F%282%2Aa%29+ we get
x=(-34+-sqrt[34^2-4*4*-50])/2*4
x=(-34+-sqrt[1156+800])/8
x=(-34+-sqrt1956)/8
x=(-34+-44.23)/8
x=(-34+44.23)/8
x=10.23/8
x=1.278 ans. for the width of the strip.
Proof:
(7+2*1.278)(10+2*1.278)=120
(7+2.556)(10+2.556)=120
9.556*12.556=120
120~120