Math Problem Statement

Find the surface area of the figure. Use 3.14 for π and round to the nearest hundredth, if necessary. The figure consists of a hemisphere with a radius of 4.5 yards on top of a cylinder with a radius of 4.5 yards and a height of 3 yards.

Solution

To solve this problem, we need to find the surface area of a figure that resembles a hemisphere (top half of a sphere) resting on top of a cylinder.

Step-by-Step Solution:

  1. Identify the dimensions:

    • The diameter of both the hemisphere and the cylinder is 99 yards, which means the radius rr is: r=92=4.5 yardsr = \frac{9}{2} = 4.5 \text{ yards}
    • The height of the cylinder is given as 33 yards.
  2. Surface Area of the Hemisphere:

    • The surface area of a hemisphere (not including the circular base) is given by: Surface Area of Hemisphere=2πr2\text{Surface Area of Hemisphere} = 2 \pi r^2
    • Using π3.14\pi \approx 3.14 and r=4.5r = 4.5: Surface Area of Hemisphere=2×3.14×(4.5)2\text{Surface Area of Hemisphere} = 2 \times 3.14 \times (4.5)^2 =2×3.14×20.25= 2 \times 3.14 \times 20.25 =127.17 square yards= 127.17 \text{ square yards}
  3. Surface Area of the Cylinder (curved part only):

    • The lateral surface area of a cylinder is given by: Lateral Surface Area of Cylinder=2πrh\text{Lateral Surface Area of Cylinder} = 2 \pi r h
    • With r=4.5r = 4.5 and h=3h = 3: Lateral Surface Area of Cylinder=2×3.14×4.5×3\text{Lateral Surface Area of Cylinder} = 2 \times 3.14 \times 4.5 \times 3 =2×3.14×13.5= 2 \times 3.14 \times 13.5 =84.78 square yards= 84.78 \text{ square yards}
  4. Total Surface Area:

    • To find the total surface area, we add the surface area of the hemisphere and the lateral surface area of the cylinder (note that the base of the hemisphere and the top of the cylinder are not included since they are internal): Total Surface Area=127.17+84.78\text{Total Surface Area} = 127.17 + 84.78 =211.95 square yards= 211.95 \text{ square yards}

Final Answer:

The surface area of the figure is approximately 211.95 square yards.

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Related Questions to Explore:

  1. How would the surface area change if the radius was doubled?
  2. What would be the volume of this combined hemisphere and cylinder?
  3. How would the calculation change if the height of the cylinder was increased to 6 yards?
  4. What is the formula for the surface area of a full sphere?
  5. How can you find the surface area if given the circumference instead of the diameter?

Tip:

For composite shapes, break down the surface area calculation by focusing on each part individually and then sum them for the total area.

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Math Problem Analysis

Mathematical Concepts

Geometry
Surface Area
Composite Solids

Formulas

Surface Area of Hemisphere = 2πr^2
Lateral Surface Area of Cylinder = 2πrh

Theorems

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Suitable Grade Level

Grade 10