Answer:
D. sum of these edges is increased by 24 inches -- True
Step-by-step explanation:
Given a cube and its edge is increased by 2 inches.
To study the effect of this increase in the Volume, area of each face, diagonal and sum of edges.
Solution:
Let the side of original cube = a inches.
Formula for volume of cube:
[tex]V =side^3 = a^3[/tex]
If the side is increased by 2 inches, the side becomes (a+2) inches.
So, new volume, [tex]V' = (a+2)^3[/tex]
Using the formula:
[tex](x+y)^3 =x^3+y^3+3xy(x+y)[/tex]
[tex]V' = (a+2)^3 = a^3+8+3\times 2 \times a(a+2)=a^3+8+6a(a+2)[/tex]
So, [tex]V' = V + 8+6a(a+2)[/tex]
Volume increased by 8+6a(a+2) [which is not equal to 8]
So, statement is false:
A. volume is increased by 8 cubic inches -- False
Each face in a cube is a square.
Area of each face, A = [tex]side^2 = a^2[/tex]
New area, A' = [tex](a+2)^2[/tex]
Using the formula: [tex](x+y)^2 =x^2+y^2+2xy[/tex]
[tex]A' = a^2+4+4a[/tex]
Area increased by 4+4a [which is not equal to 4 sq inches]
B. area of each face is increased by 4 square inches -- False
Diagonal of each face = [tex]a\sqrt2[/tex]
Increase of 2 in the edge:
New diagonal = [tex](a+2)\sqrt2 = a\sqrt2+2\sqrt2[/tex]
So, increase of [tex]2\sqrt2[/tex] not 2.
C. diagonals of each face is increased by 2 inches -- False
There are 12 number of edges in a square.
So sum of all 12 edges = 12a
When edge is increased by 2, sum of all edges = 12(a+2) = 12a + 24
An increase of 24.
D. sum of these edges is increased by 24 inches -- True
