Math Problem Statement

find the total surface area of a solid hemisphere of radius 7 cm. (Take it to be 3.142)

Solution

To find the total surface area of a solid hemisphere, we need to consider both the curved surface area and the flat circular base of the hemisphere.

Step-by-Step Solution

  1. Curved Surface Area of Hemisphere:

    The formula for the curved surface area of a hemisphere is:

    Curved Surface Area=2πr2\text{Curved Surface Area} = 2 \pi r^2

  2. Area of the Base:

    The base of the hemisphere is a circle with the same radius rr. The area of the base is:

    Base Area=πr2\text{Base Area} = \pi r^2

  3. Total Surface Area of the Hemisphere:

    The total surface area is the sum of the curved surface area and the base area:

    Total Surface Area=2πr2+πr2=3πr2\text{Total Surface Area} = 2 \pi r^2 + \pi r^2 = 3 \pi r^2

    Now, substitute the given values:

    r=7cm,π=3.142r = 7 \, \text{cm}, \quad \pi = 3.142

    So,

    Total Surface Area=3×3.142×(7)2\text{Total Surface Area} = 3 \times 3.142 \times (7)^2

    Calculate 727^2:

    72=497^2 = 49

    Now substitute this value:

    Total Surface Area=3×3.142×49\text{Total Surface Area} = 3 \times 3.142 \times 49

    Compute the multiplication:

    Total Surface Area=3×154.958=464.874cm2\text{Total Surface Area} = 3 \times 154.958 = 464.874 \, \text{cm}^2

Final Answer

The total surface area of the solid hemisphere is 464.874 cm².

Would you like further details or have any questions?

Here are 5 related questions to expand your understanding:

  1. How would the surface area change if the radius were doubled?
  2. What is the volume of a hemisphere with the same radius?
  3. How do you find the surface area of a hollow hemisphere?
  4. How does the use of different values for π\pi affect the calculation?
  5. Can you derive the formula for the surface area of a hemisphere from scratch?

Tip: Remember that for surface area calculations, always double-check which parts of the solid are included (like bases or curves) in the final measurement.

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Math Problem Analysis

Mathematical Concepts

Geometry
Surface Area
Solid Figures

Formulas

Curved Surface Area of Hemisphere = 2πr^2
Base Area of Hemisphere = πr^2
Total Surface Area of Hemisphere = 3πr^2

Theorems

Surface Area Theorem for Solid Figures

Suitable Grade Level

Grades 8-10