Saturday

August 30, 2014

August 30, 2014

Posted by **Abi** on Thursday, June 13, 2013 at 10:05am.

a) Draw a figure that visually represents the problem. Let x and y represent the length and width of the rectangular region respectively

b) Determine the radius of the semicircular ends of the track. Determine the distance, in terms of y, around the inside edge of each semicircular part of the track.

c) Use the result of part b to write an equation in terms of x and y, for the distance traveled in one lap around the track. Solve for x.

d) Use the result of part c to write the area A of the rectangular region as a function of x. What dimensions will produce a rectangle of maximum area?

- Precal -
**Reiny**, Thursday, June 13, 2013 at 12:14pma) ---- you have done that, I hope

b) radius = y/2

( I would have labeled the radius y, making the width of the rectangle 2y, that way I would have no fractions, but ..... oh well)

So we have two semicircles or one complete circle with radius y/2

distance around = circumference of one circle

= 2π(y/2) = πy

c) so 2x + πy = 200

x = (200 - πy)/2

Area = π(y/2)^2 + xy

= πy^2/4 + y(200-πy)/2

= πy^2 /4 + 100y - (π/2)y^2

d(area)/dy = πy/2 + 100 - πy

= 0 for a max/min of area

πy - πy/2 = 100

πy/2 = 100

y = 200/π

then x = (200 - π(200/π)/2 = 0

ahh, the famously flawed track question.

Of course the answer makes sense. It says to simply build a circular track, since a circle gives us the largest area for a given perimeter.

But in most of the variations of this question, there is some other restriction given on your values of x and y.

**Related Questions**

Calculus - An indoor physical fitness room consists of a rectangular region with...

Pre-Calculus - An indoor physical fitness room consists of a rectangular region ...

Precal - An indoor physical fitness room consists of a rectangular region with a...

Algebra - Please help me with this algebra question?!?!?!? Find the discriminant...

Math - An indoor running track has the dimensions shown. The ends of the track ...

math - the lenght of a rectangular room is 6 feet longer than twice the width. ...

Math - A rectangular room has a perimeter of 94 and area of 546. What are the ...

Math - An indoor track is shaped like a rectangle with a semi-circle on each end...

Fher - a laundry room is shaped like a rectangle. the area of the room is 6 ...

Math - The Wilson family is at it again.. they are installing new carpet for ...