Answer:
width = length = 3 inches
height = 7 inches
Step-by-step explanation:
If x is the width and length of the base, and y is the height, then:
y = x + 4
The volume of the box is:
63 = x²y
The surface area of the box is:
93 = x² + 4xy
Substitute the first equation into the third.
93 = x² + 4x (x + 4)
93 = x² + 4x² + 16x
0 = 5x² + 16x − 93
0 = (x − 3) (5x + 31)
x = 3
y = 7
Use the second equation to check your answer.
63 = (3)²(7)
63 = 63
Answer:
Length=Width=3
Height=7.
Step-by-step explanation:
First, let's write some equations. So, we have an open box (with no lid) that has a square base. It has a height 4 units more of its width/length.
First, let's write the equation for the volume. The volume of a rectangular prism is:
[tex]V=lwh[/tex]
Recall that we have a square base. In other words, the length and width are exactly the same. Therefore, we can do the following substitution:
[tex]V=(w)wh=w^2(h)[/tex]
Now, recall that the height is four units more than the width/length. Therefore, we can make the following substitution:
[tex]V=w^2(w+4)\\63=w^2(w+4)[/tex]
We can't really do anything with this. Let's next find the equation for the surface area.
So, we have 5 sides (not 6 because we have no lid). The bottom side is a square, so it's area is w^2. Since we have a square base, the remaining four sides will have an area w(w+4). In other words:
[tex]93=w^2+4(w(w+4))[/tex]
The left term represents the area of the square base. The right term represents the area of one of the rectangular sides, times sides meaning four sides. Simplify:
[tex]93=w^2+4w^2+16w\\5w^2+16w-93=0[/tex]
This seems solvable. Let's try it. Trying factoring by guessing and checking.
We can see that it is indeed factor-able. -15 and 31 are the numbers:
[tex]5w^2-15w+31w-93=0\\5w(w-3)+31(w-3)=0\\(5w+3)(w-3)=0\\w=3\\h=w+4=7[/tex]
We ignore the other one because width cannot be negative.
So, the width/length is 3 and the height is 7. We can check this by plugging this into the volume formula:
[tex]63\stackrel{?}{=}(3)^2(7)\\63\stackrel{\checkmark}{=}63[/tex]
