# Thread: Cubic and Quartic Functions Problems: Part 3

1. ## Cubic and Quartic Functions Problems: Part 3

I am having trouble with a couple of questions in terms of the proccess of solving the questions:
4 A cuboid (recatangular prisim) has dimensions x metres, h metres and 4x metres. The cuboid is made of 640m of wire
a Find h in terms of x
b Find the volume, Vm^3 of the cuboid in terms of x
c Find V when x = 11
d Find the possible values of x for the cuboid to exist
e Find the possible values of x when V = 60,000 (give 2 decimal places)
f Find the max volume of the cuboid and the value of x for which it occurs

That is a long list of questions, and I will be greatly apprecieated if any of you would have the time to help and explain these questions for me.

2. Originally Posted by theleontan
I am having trouble with a couple of questions in terms of the proccess of solving the questions:
4 A cuboid (recatangular prisim) has dimensions x metres, h metres and 4x metres. The cuboid is made of 640m of wire
a Find h in terms of x
b Find the volume, Vm^3 of the cuboid in terms of x
c Find V when x = 11
d Find the possible values of x for the cuboid to exist
e Find the possible values of x when V = 60,000 (give 2 decimal places)
f Find the max volume of the cuboid and the value of x for which it occurs

That is a long list of questions, and I will be greatly apprecieated if any of you would have the time to help and explain these questions for me.
1. Draw a sketch! (see attachment)

2. The cuboid contains the edges x, 4x and h four times each. Since all edges together have a length of 640 m you already know:

$4 \cdot x + 4 \cdot 4x + 4 \cdot h = 640~\implies~5x+h=160$