Math Problem Statement

Shape A and shape B are two similar solid shapes. The ratio of the volume of shape A to the volume of shape B is 1:10

The surface area of shape B is 72 cm^2

Work out the surface area of shape A. Give your answer correct to 3 significant figures.

Solution

Since shapes A and B are similar, the relationship between their volumes and surface areas follows certain proportionalities based on their linear scale factor.

Step 1: Relationship between volumes

The ratio of the volumes of two similar shapes is the cube of the ratio of their corresponding linear dimensions. The given volume ratio is:

Volume of shape AVolume of shape B=110\frac{\text{Volume of shape A}}{\text{Volume of shape B}} = \frac{1}{10}

Thus, the linear scale factor between the shapes is the cube root of the volume ratio:

[ \text{Linear scale factor} = \sqrt[3]{\frac{1}{10}} = \frac{1}{\sqrt[3]{10}} ]

Step 2: Relationship between surface areas

The surface areas of similar shapes are proportional to the square of the linear scale factor. So, the ratio of the surface areas is:

[ \frac{\text{Surface area of shape A}}{\text{Surface area of shape B}} = \left(\frac{1}{\sqrt[3]{10}}\right)^2 = \frac{1}{\sqrt[3]{100}} ]

Step 3: Calculate the surface area of shape A

We know the surface area of shape B is 72 cm², so the surface area of shape A can be calculated as:

Surface area of shape A=72×11003\text{Surface area of shape A} = 72 \times \frac{1}{\sqrt[3]{100}}

Now, let's compute this expression.

10034.6416\sqrt[3]{100} \approx 4.6416

Surface area of shape A=724.6416272×0.046413.345\text{Surface area of shape A} = \frac{72}{4.6416^2} \approx 72 \times 0.04641 \approx 3.345

Thus, the surface area of shape A is approximately:

3.35cm2\boxed{3.35 \, \text{cm}^2}

Do you have any questions, or would you like further details?

Here are 5 related questions:

  1. How do we derive the linear scale factor from the volume ratio?
  2. Can you calculate the surface area ratio if the volume ratio were 1:27?
  3. What happens to the surface area if the volume of shape A is doubled?
  4. How does the surface area relate to the volume in similar 3D shapes?
  5. Can you find the linear scale factor if the surface area ratio is given instead of the volume ratio?

Tip: Always remember that the ratio of surface areas of similar shapes is the square of the ratio of their linear dimensions!

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Math Problem Analysis

Mathematical Concepts

Geometry
Similar Shapes
Ratio and Proportion
Surface Area
Volume

Formulas

Volume Ratio = (Linear Scale Factor)^3
Surface Area Ratio = (Linear Scale Factor)^2

Theorems

Similarity Theorem
Proportionality in Similar Shapes

Suitable Grade Level

Grades 9-11