Chapter 49: Problem 853
If a cube has edge length a, what happens to (a) the cube's surface area as a is increased by a factor \(x ?\) b) the cube's volume as a is increased by a factor \(\mathrm{x}\) ?
Short Answer
Expert verified
a) When the edge length of a cube is increased by a factor of x, the surface area is increased by a factor of \(x^2\).
b) When the edge length of a cube is increased by a factor of x, the volume is increased by a factor of \(x^3\).
Step by step solution
01
Understanding the problem
We need to know the formulas of the surface area and volume of a cube when the edge length is a.
02
Surface Area formula
The surface area (S) of a cube with edge length a can be calculated using the formula: \(S = 6a^2\) (since a cube has 6 equal faces, and each face is a square, so each face has an area of \(a^2\))
03
Volume formula
The volume (V) of a cube with edge length a can be calculated using the formula: \(V = a^3\) (since the volume of a cube is the product of the edge lengths, and all three edge lengths are equal)
04
Calculate the surface area when edge length is increased by a factor of x
When the edge length is increased by a factor of x, the new edge length will be ax. We substitute this new length into the surface area formula:
\(S' = 6(ax)^2\)
\(S' = 6a^2x^2\)
Comparing the original surface area formula (\(S = 6a^2\)) and the new surface area formula (\(S' = 6a^2x^2\)), we can see that the surface area is increased by a factor of \(x^2\) when the edge length is increased by a factor of x.
05
Calculate the volume when edge length is increased by a factor of x
Similar to Step 4, we will now substitute the new edge length (ax) into the volume formula:
\(V' = (ax)^3\)
\(V' = a^3x^3\)
Comparing the original volume formula (\(V = a^3\)) and the new volume formula (\(V' = a^3x^3\)), we can see that the volume increases by a factor of \(x^3\) when the edge length is increased by a factor of x.
06
Conclusion
a) When the edge length of a cube is increased by a factor of x, the surface area is increased by a factor of \(x^2\).
b) When the edge length of a cube is increased by a factor of x, the volume is increased by a factor of \(x^3\).
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Surface Area of a Cube
When we think about the surface area of a cube, imagine unwrapping it like a box. You'll find it has six equal square faces. Since each face has an area of \(a^2\) where \(a\) is the length of the edge, the total surface area is calculated as \(S = 6a^2\). This formula is derived from the fact that all six squares are exactly the same in a cube.
But what happens if you change the length of the edge? If the edge length is multiplied by a factor \(x\), the new length becomes \(ax\) and the modified surface area becomes \(S' = 6(ax)^2 = 6a^2x^2\).
But what happens if you change the length of the edge? If the edge length is multiplied by a factor \(x\), the new length becomes \(ax\) and the modified surface area becomes \(S' = 6(ax)^2 = 6a^2x^2\).
- The surface area increases by a factor of \(x^2\).
Volume of a Cube
A cube's volume represents the three-dimensional space it occupies. It's found by taking the edge length \(a\) and using the formula \(V = a^3\). This is because all dimensions of a cube (length, width, height) are equal.
Now, if the edge length increases by a factor \(x\), what happens to the volume? The new edge length is \(ax\), leading to a revised volume of \(V' = (ax)^3 = a^3x^3\).
Now, if the edge length increases by a factor \(x\), what happens to the volume? The new edge length is \(ax\), leading to a revised volume of \(V' = (ax)^3 = a^3x^3\).
- The volume increases by a factor of \(x^3\).
Mathematical Formulas
Mathematics provides us with formulas to generalize and simplify the calculation of properties like surface area and volume. For a cube:
Understanding these formulas is crucial because they help explain geometric properties in a straightforward way, avoiding complex individual calculations.
- Surface Area: \(S = 6a^2\)
- Volume: \(V = a^3\)
Understanding these formulas is crucial because they help explain geometric properties in a straightforward way, avoiding complex individual calculations.
Scaling in Geometry
Scaling is a fundamental concept in geometry which involves expanding or contracting the size of an object. When the size of an object's dimensions are multiplied by a factor of \(x\), different properties scale differently depending on their nature.
For a cube:
For a cube:
- When the dimensions of an object are increased by a factor of \(x\), the surface area, being two-dimensional, scales by \(x^2\).
- In contrast, the volume, being three-dimensional, scales by \(x^3\).