Homework Help: Math: Calculus

Posted by REALLY NEED HELP!!! on Monday, November 1, 2010 at 5:46pm.

A fence is to be built to enclose a rectangular area of 230 square feet. The fence along three sides is to be made of material that costs 5 dollars per foot, and the material for the fourth side costs 15 dollars per foot. Find the dimensions of the enclosure that is most economical to construct.

Math: Calculus - REALLY NEED HELP!!!, Monday, November 1, 2010 at 5:50pm
My dimensions that I got is sqrt(215.625)*230/sqrt(215.625) but it's wrong.
Math: Calculus - Damon, Monday, November 1, 2010 at 5:53pm
cost = 5(2b+L) + 15 L = 10 b + 20 L
bL = 230 so b = 230/L

cost = 2300/L + 20 L

d cost/dL = -2300/L^2 + 20 L

= 0 for min
20 L = 2300/L^2
L ^3 = 115
L = 4.86
b = 47.3
check my arithmetic !!!
error - Damon, Monday, November 1, 2010 at 5:55pm
cost = 5(2b+L) + 15 L = 10 b + 20 L
bL = 230 so b = 230/L

cost = 2300/L + 20 L

d cost/dL = -2300/L^2 + 20 *******

= 0 for min
20 = 2300/L^2
L ^2 = 115
L = 10.72
b = 21.5
b = 47.3
Math: Calculus - bobpursley, Monday, November 1, 2010 at 5:59pm
cost=5*(2w+L)+15L

Area= Lw or w= ARea/L=230/L

cost= 10(230/L)+5L+15L

dcost/dL= -2300/L^2+20=0
L=sqrt 115 and w= 230/sqrt115

Answer this Question

Related Questions

Calculus 1 - A fence is to be built to enclose a rectangular area of 220 square ...
calculus - A fence is to be built to enclose a rectangular area of 210 square ...
Calculus - A fence is to be built to enclose a rectangular area of 280 square ...
Math - A fence is to be built to enclose a rectangular area of 200 square feet. ...
PreCalculus - Three sides of a fence and an existing wall form a rectangular ...
Math - A farmer has 230 ft of fence to enclose a rectangular garden. What is the...
calculus - A rancher wants to fence in an area of 3000000 square feet in a ...
Math - A rectangular study area is to be enclosed by a fence and divided into ...
Calculus - A rancher wants to fence in an area of 500000 square feet in a ...
Calculus - A rancher wants to fence in an area of 5189400 square feet in a ...

For Further Reading

First Name:
School Subject:
Answer: