The owner of the Rancho Grande has 3020 yd of fencing with which to enclose a rectangular piece of grazing land situated along the straight portion of a river. If fencing is not required along the river, what are the dimensions of the largest area he can enclose?
shorter side yd
longer side yd

What is this area?
yd2

Respuesta :

Answer:

Shorter side = 755 yd

longer side   = 1510 yd  

A(max)  = 1140050 yd²

Step-by-step explanation:

The owner has 3020 yd of fencing

Lets assume:

x the shorter side of the rectangle ( we will use fencing in two sides of length x )

y the longer one

A area of the rectangle          and P the perimeter of the rectangle ( we have only three sides covered by fencing material)

We have:       A = x * y          P = 2 * x + y   ⇒  y  = P - 2*x  ⇒  y  = 3020 - 2* x

A (x) = x * ( 3020 - 2*x)  ⇒  A(x) = 3020 * x - 2* x²

Taken derivative

A´(x) = 3020 - 4 * x

If     A´(x) = 0               3020 -4*x = 0     ⇒4*x = 3020    x =  755 yd

If we take second derivative A´´(x)  = -4

so  A´´(x) < 0 so there is a maximun in point x = 755

Then

Rectangle dimensions :

x = 755 yd        ⇒  y = 3020 - 2 * x   ⇒ y = 3020 - 2 * (755)     y = 1510 yd

Maximum area is :  A(max)  = 1510 * 755  ⇒ A(max)  = 1140050 yd²

The largest area he can enclose is 1,013,374 yards², across 4 equal sides of 1,006.66 yards.

Since the owner of the Rancho Grande has 3020 yd of fencing with which to enclose a rectangular piece of grazing land situated along the straight portion of a river, to determine, if fencing is not required along the river, what are the dimensions of the largest area he can enclose, the following calculations must be performed:

  • 3020/3 x 2 = 2013.33
  • 1513.33 x 500 = 756,665
  • 1413.33 x 600 = 847,998
  • 1313.33 x 700 = 919,331
  • 1213.33 x 800 = 970,664
  • 1113.33 x 900 = 1,001,997
  • 1013.33 x 1000 = 1,013,330
  • 1006.66 x 1006.66 = 1,013,374

Therefore, the largest area he can enclose is 1,013,374 yards², across 4 equal sides of 1,006.66 yards.

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