Respuesta :
Given:
Edge of a cubic box = n inches.
He decided to make the box 1 inch taller and 2 inches longer, while keeping its depth at n inches.
To find:
How many cubic inches greater than the box he originally planned to build?
Solution:
Edge of a cubic box is n inches, so the volume of the original cube is:
[tex]V_1=(edge)^3[/tex]
[tex]V_1=n^3[/tex]
According to the given information,
New width of the box = n+1
New length of the box = n+2
New height of the box = n
So, the volume of the new box is:
[tex]V_2=Length\times width\times h[/tex]
[tex]V_2=(n+2)(n+1)n[/tex]
[tex]V_2=(n^2+2n+n+2)n[/tex]
[tex]V_2=(n^2+3n+2)n[/tex]
[tex]V_2=n^3+3n^2+2n[/tex]
Now, the difference between new volume and original volume is:
[tex]V_2-V_1=n^3+3n^2+2n-n^3[/tex]
[tex]V_2-V_1=3n^2+2n[/tex]
So, the volume of new box is 3n^2+2n cubic inches more than the original box.
Therefore, the correct option is A.
