Calculate Cube Volume: Effects of Adding 6 Units to Side Length

Question

If we increase the side of a cube by 6, how many times will the volume of the cube increase by?

Video Solution

Solution Steps

00:00 If we multiply the cube's edge by 6, by how much does the volume increase?
00:03 We multiplied the cube's edge by 6
00:07 Let's use the formula for calculating cube volume (edge cubed)
00:13 This is the cube volume expression
00:17 Let's find the cube volume expression when multiplied by 6
00:27 This is the cube volume expression
00:30 Let's notice the coefficient of X cubed, this shows how much the volume increased
00:37 And this is the solution to the question

Step-by-Step Solution

Let's denote the initial cube's edge length as x,

The formula for the volume of a cube with edge length b is:

V=b3 V=b^3

Therefore the volume of the initial cube (meaning before increasing its edge) is:

V1=x3 V_1=x^3

Proceed to increase the cube's edge by a factor of 6, meaning the edge length is now: 6x . Therefore the volume of the new cube is:

V2=(6x)3=63x3 V_2=(6x)^3=6^3x^3

In the second step we simplified the expression for the new cube's volume by using the power rule for multiplication in parentheses:

(zy)n=znyn (z\cdot y)^n=z^n\cdot y^n

We applied the power to each term inside of the parentheses multiplication.

Next we'll answer the question that was asked - "By what factor did the cube's volume increase", meaning - by what factor do we multiply the old cube's volume (before increasing its edge) to obtain the new cube's volume?

Therefore to answer this question we simply divide the new cube's volume by the old cube's volume:

V2V1=63x3x3=63 \frac{V_2}{V_1}=\frac{6^3x^3}{x^3}=6^3

In the first step we substituted the expressions for the volumes of the old and new cubes that we obtained above. In the second step we reduced the common factor between the numerator and denominator,

Therefore we understood that the cube's volume increased by a factor of -63 6^3 when we increased its edge by a factor of 6,

The correct answer is b.

Answer

63 6^3