# Stuck on Two Word Problems/ Functions

• September 16th 2008, 12:02 PM
emximer
Stuck on Two Word Problems/ Functions
1."The combination of cold temperatures and wind speed determine what is called wind chill. The wind chill is a temperature that is the still-air equivalent of the combination of cold and wind. When the Wind speed is 25mph, the wind chill depends on the temperature t (in degrees Fahrenheit) according to

WC= 1.479t - 43.821

For what temp does it feel at least 30 degrees colder than teh air temp? That is, find t such that WC <=(less than or equal to) t -30

Don't really have any idea on how to do that one, I tried graphing it on my graphing calcualtor but just confused myself.

2. A shipping crate has a square base with sides of length x feet and it is half as tall as it is wide. If the material for the bottom and sides of the box cost 2\$ per sqr foot and the material for the top cost 1.50 per sqr ft., express the total cost of materials for the box as a function of x.

So I know the length = x and the height = .5x
So the area of the sides is x(.5x) times 4 would give me the area for the sides in sqr feet? and to do the bottom I'd just do x times x and the same with the top? I'm not sure hwo to put it all together though
• September 16th 2008, 12:17 PM
icemanfan
For the first problem, you're making it more complicated than it is. What you want is to find the temperature at which the wind chill changes the temperature felt by at least 30 degrees less, so solve the equation for the desired change: $1.479t - 43.821 = -30$

For the second problem, you will multiply each side (represented by a number in square feet) by the cost per square foot for that side, and then add those numbers together to determine the total cost. The trick is that the top's cost is $1.5x^2$, whereas the bottom's cost is $2x^2$.
• September 16th 2008, 01:28 PM
emximer
Quote:

Originally Posted by icemanfan
For the first problem, you're making it more complicated than it is. What you want is to find the temperature at which the wind chill changes the temperature felt by at least 30 degrees less, so solve the equation for the desired change: $1.479t - 43.821 = -30$

For the second problem, you will multiply each side (represented by a number in square feet) by the cost per square foot for that side, and then add those numbers together to determine the total cost. The trick is that the top's cost is $1.5x^2$, whereas the bottom's cost is $2x^2$.

Ok I got the answer for the first one t=9.345 degrees

for the 2nd one I got f(x) = 3.5x^2 + 4x

do these look right?