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Surface Areas and Volumes Test - 39

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Surface Areas and Volumes Test - 39
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  • Question 1
    1 / -0
    Calculate the volume of a sphere whose radius is $$3 \text{ cm}$$.
    Solution
    Formula: Volume of sphere =$$\dfrac{4}{3} \pi r^3$$
    Where, $$r=radius$$

    Given:
    $$r=3\text{ cm}$$

    Substitute the value of $$r$$ in the above formula,
    $$\dfrac{4}{3} \pi  r^3=\dfrac{4}{3}\times3.14\times3^3$$
               $$=\dfrac{4}{3}\times3\times3\times3\times \pi$$
               $$=\dfrac{4}{3}\times27\times\pi$$
               $$=\dfrac{108}{3}\times\pi$$
               $$=36\pi\text{ cm}^3$$
  • Question 2
    1 / -0
    What is the volume of a sphere given: (Use $$\displaystyle \pi =3.14$$)

    Solution
    Using formula for volume of sphere =$$\dfrac{4}{3} \pi r^3$$
    $$r=radius$$
    Given: $$radius(r)=30\ m$$
    $$\Rightarrow \dfrac{4}{3} \pi  r^3=\dfrac{4}{3} \times 3.14 \times 30^3$$
                 $$=\dfrac{4}{3} \times 30 \times 30 \times 30 \times 3.14$$
                 $$=\dfrac{4}{3} \times 27000 \times 3.14$$
                 $$=\dfrac{339120}{3}$$
                 $$=113040\ m^3$$
  • Question 3
    1 / -0
    The volume of sphere is $$\displaystyle 904.77{ cm }^{ 3 }$$. Find its radius. (Round off your answer to the nearest whole number).
    Solution
    Formula:
    Volume of sphere$$=\dfrac{4}{3}\pi r^3$$
    where,
    $$r=radius$$
    Given:
    $$volume=904.77\ cm^3$$
    After substituting the values in the formula we gte:
    $$904.77= \dfrac{4}{3}\pi r^3$$

    $$\Rightarrow 904.77= \dfrac{4}{3}\times3.14\times r^3$$

    $$\Rightarrow \dfrac{904.77\times3}{4\times3.14}=r^3$$

    $$\Rightarrow r^3=\dfrac{2714.31}{12.56}$$
    $$\Rightarrow r^3=215.42 \approx 216$$
    $$\Rightarrow r=\sqrt[3]{216}$$
    $$\Rightarrow r=6\ cm$$
  • Question 4
    1 / -0
    Calculate the volume of a sphere whose radius is $$12$$ m.
    Solution
    Formula:
    Volume of sphere =$$\dfrac{4}{3} \pi r^3$$
    $$r=radius$$
    Given:
    $$r=12\ m$$
    $$\Rightarrow \dfrac{4}{3} \pi  r^3=\dfrac{4}{3}*3.14*12^3$$
    $$=\dfrac{4}{3}*12*12*12* 3.14$$
    $$=\dfrac{4}{3}*1728*3.14$$
    $$=\dfrac{21703.68}{3}$$
    $$=7234.56\ m^3$$
  • Question 5
    1 / -0
    What is the diameter of the spherical ball whose volume is $$\displaystyle 268.08{ mm }^{ 3 }$$. (use $$\displaystyle \pi =3.14$$). Round off your answer to nearest whole number.
    Solution
    Formula:
    Volume of sphere$$=\dfrac{4}{3}\pi r^3$$
    where,
    $$r=radius$$
    Given:
    $$volume=268.08 mm^3$$
    Substituting the values in the given formula we get:
    $$ 268.08= \dfrac{4}{3}\pi r^3$$

    $$\Rightarrow 268.08= \dfrac{4}{3}\times3.14\times r^3$$

    $$\Rightarrow \dfrac{268.08\times3}{4\times 3.14}=r^3$$

    $$\Rightarrow r^3=\dfrac{804.28}{12.56}$$
    $$\Rightarrow r^3=64.03 \approx 64$$
    $$\Rightarrow r=\sqrt[3]{64}$$
    $$\Rightarrow r=4\ mm$$
    Thus, the diameter $$=2r=8\ mm$$.
  • Question 6
    1 / -0
    The volume of a sphere is $$\displaystyle 300\pi { cm }^{ 3 }$$. Find its radius.
    Solution
    Formula:
    Volume of sphere$$=\dfrac{4}{3}\pi r^3$$
    where,
    $$r=radius$$
    Given:
    $$volume=300\pi cm^3$$
    After sustituting the values in the formula we get:
    $$ 300\pi= \dfrac{4}{3}\pi r^3$$
    $$\Rightarrow 300= \dfrac{4}{3} r^3$$($$\pi$$ gets cancelled from both the sides)

    $$\Rightarrow \dfrac{300*3}{4}=  r^3$$
    $$\Rightarrow r^3=\dfrac{900}{4}$$

    $$\Rightarrow r^3=225$$
    $$\Rightarrow r=\sqrt[3]{225}$$
    $$\Rightarrow r=6.08\ cm$$
  • Question 7
    1 / -0
    Find the volume of a sphere whose diameter is $$10$$ in.
    Solution
    Formula:
    Volume of sphere =$$\dfrac{4}{3} \pi r^3$$
    $$r=radius$$
    Given:
    $$diameter(d)=10\ in$$
    $$radius(r)=\dfrac{d}{2}=\dfrac{10}{2}=5\ in$$
    $$\Rightarrow \dfrac{4}{3} \pi  r^3=\dfrac{4}{3}*3.14*5^3$$
    $$=\dfrac{4}{3}*5*5*5*3.14$$
    $$=\dfrac{4}{3}*125*3.14$$
    $$=\dfrac{1570}{3}$$
    $$=523.33\ in^3$$
  • Question 8
    1 / -0
    The volume of a sphere is $$\displaystyle 4000\pi { m }^{ 3 }$$. Find its surface area. (use $$\displaystyle \pi =\pi $$.)
    Solution
    Volume of sphere $$\displaystyle =\frac { 4 }{ 3 } \pi { r }^{ 3 }$$
    $$\Rightarrow \displaystyle 4000\pi =\frac { 4 }{ 3 } \times \pi \times { r }^{ 3 }$$
    $$\Rightarrow \displaystyle \dfrac {{ 4000\times 3   }}{{ 4 }}={ r }^{ 3 }$$
    $$\Rightarrow \displaystyle \dfrac {12000}{4}={ r }^{ 3 }$$
    $$\Rightarrow \displaystyle { r }^{ 3 }=3000$$
    $$\Rightarrow \displaystyle r=\sqrt [ 3 ]{ 3000 } $$
    $$\Rightarrow \displaystyle r=14.42$$
    Surface area of sphere $$\displaystyle =4\pi { r }^{ 2 }$$
    $$\displaystyle =4\times \pi \times 14.42\times 14.42$$
    $$\displaystyle =2611.68{ m }^{ 2 }$$
  • Question 9
    1 / -0
    Find the volume of a hemisphere whose radius is $$7$$ cm. (use $$\displaystyle \pi =\frac { 22 }{ 7 } $$)
    Solution
    Given, radius of hemisphere $$=7$$ cm
    Volume of hemisphere $$\displaystyle =\frac { 2 }{ 3 } \pi { r }^{ 3 }$$
    $$\displaystyle =\frac { 2 }{ 3 } \times \frac { 22 }{ 7 } \times 7\times 7\times 7$$
    $$\displaystyle =718.66{ cm }^{ 3 }$$
  • Question 10
    1 / -0
    Calculate the surface area and volume of the sphere with diameter $$0.8$$ in (use $$\displaystyle \pi =3$$).
    Solution

    $$\displaystyle \therefore $$ radius $$=0.4$$
    Volume of sphere $$\displaystyle =\frac { 4 }{ 3 } \pi { r }^{ 3 }$$
    $$\displaystyle =\frac { 4 }{ 3 } \times 3\times 0.4\times 0.4\times 0.4$$
    $$\displaystyle =0.256{ in }^{ 3 }$$
    Surface area of a sphere $$\displaystyle =4\pi { r }^{ 2 }$$
    $$\displaystyle =4\times 3\times 0.4\times .4$$
    $$\displaystyle =1.92{\  in }^{ 2 }$$
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