Core Connections: Course 3
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Core Connections: Course 3 View details
1. Section 10.1
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Exercise 13 Page 459

Practice makes perfect
We are told that the volume of a cube is 125 cubic inches. We want to find the length of its sides. Let's visualize the situation by drawing a cube and letting s be the length of its sides.
cube
When we find the volume of a prism, we multiply its three side measurements — the length, the width, and the height — which all happen to be the same for a cube. Recall that multiplying a number by itself three times is equal to raising the number to the power of 3. V= s* s* s ⇔ V= s^3 Since we already know that the volume is 125 cubic inches, we will substitute this value for V in the above equation. Then we can solve for s by taking the cube root of both sides of the equation. Let's do it!
V=s^3
125=s^3
Solve for s
sqrt(125)=sqrt(s^3)
sqrt(5* 5* 5)=sqrt(s^3)
sqrt(5^3)=sqrt(s^3)
5=s
s=5
The length of each side of a cube with a volume of 125 cubic inches is 5 inches.
To calculate the surface area of a prism, we can use the following formula. S=2(l w+l h+wh) The terms inside the parentheses represents the area of one of the three possibly different-sized faces. Each term is multiplied by 2 because opposite faces in a rectangular prism have equal dimensions. In our case, all the dimensions have the same length s because our prism is a cube. S=2(s^2+s^2+s^2) → S=6s^2 This is the formula for the surface area of a cube. Since s=5, let's substitute this value into our new formula to calculate S.
S=6s^2
S=6( 5^2)
S=6(25)
S=150
The surface area is 150 square inches.