Math Problem Statement

The surface area of sphere A is 16 times that of sphere B.

(a) Find the ratio of the diameter of sphere A to that of sphere B.

(b) Find the ratio of the volume of sphere A to that of sphere B.

Solution

The relationship between the surface area, diameter, and volume of spheres can be derived using the standard formulas:

  • Surface area of a sphere: S=4πr2S = 4\pi r^2
  • Volume of a sphere: V=43πr3V = \frac{4}{3}\pi r^3
  • Diameter: d=2rd = 2r

(a) Ratio of diameters

Let the radii of spheres A and B be rAr_A and rBr_B, respectively.

If the surface area of sphere A is 16 times that of sphere B: SA=16SBor4πrA2=16(4πrB2)S_A = 16S_B \quad \text{or} \quad 4\pi r_A^2 = 16(4\pi r_B^2)

Simplifying: rA2=16rB2rA=4rBr_A^2 = 16r_B^2 \quad \Rightarrow \quad r_A = 4r_B

Since diameter d=2rd = 2r: dAdB=2rA2rB=rArB=4\frac{d_A}{d_B} = \frac{2r_A}{2r_B} = \frac{r_A}{r_B} = 4

Thus, the ratio of the diameters is: 4:1\boxed{4:1}


(b) Ratio of volumes

Using the volume formula V=43πr3V = \frac{4}{3}\pi r^3, the ratio of the volumes is: VAVB=43πrA343πrB3=rA3rB3\frac{V_A}{V_B} = \frac{\frac{4}{3}\pi r_A^3}{\frac{4}{3}\pi r_B^3} = \frac{r_A^3}{r_B^3}

From part (a), rA=4rBr_A = 4r_B: VAVB=(4rB)3rB3=64rB3rB3=64\frac{V_A}{V_B} = \frac{(4r_B)^3}{r_B^3} = \frac{64r_B^3}{r_B^3} = 64

Thus, the ratio of the volumes is: 64:1\boxed{64:1}


Summary of Results:

(a) The ratio of diameters is 4:1\boxed{4:1}.
(b) The ratio of volumes is 64:1\boxed{64:1}.

Would you like further explanations or assistance? Here are 5 related questions to deepen your understanding:

  1. What happens to the surface area if the diameter of a sphere is doubled?
  2. How does the ratio of volumes change if the ratio of radii is 3:13:1?
  3. Derive the formula for surface area in terms of diameter rather than radius.
  4. How would you calculate the ratio of circumferences for the two spheres?
  5. If sphere B has a radius of 5 cm, what is the radius of sphere A?

Tip: Remember that surface area scales with the square of the radius, while volume scales with the cube of the radius!

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Math Problem Analysis

Mathematical Concepts

Geometry
Sphere properties
Ratios and proportions

Formulas

Surface area of a sphere: S = 4πr²
Volume of a sphere: V = (4/3)πr³
Diameter of a sphere: d = 2r

Theorems

The surface area of a sphere is proportional to the square of its radius.
The volume of a sphere is proportional to the cube of its radius.

Suitable Grade Level

Grades 9-12