Exercise 50 Page 739

Let's analyze the given figure.

The solid consists of three smaller ones.

• A cylinder with a radius of r= 2 cm and a height of h=2.5 cm.
• Two hemispheres with a radius of r= 2 cm.

  We are asked to find the volume and the surface area of the above solid. First, let's find the volume.

  Volume

  Let's use the formula for the volume of a sphere and for the volume of a cylinder.

  Solid	Cylinder	Hemisphere
  Radius	r= 2	r= 2
  Height	h= 2.5	-
  Volume	V=π r^2 h	V=1/2*4/3π r^3
  	V_1=π ( 2)^2( 2.5)= 10π	V_2=1/2*4/3π ( 2)^3= 16/3π

  The volume of the cylinder is 10π cubic inches, and the volume of the hemisphere is 163π cubic inches. Now, let's the volume of the given composite solid, V_\text{solid}.
  V_\text{solid}={\color{#FD9000}{V_1}}+2{\color{#A800DD}{V_2}}

  ▼

  Substitute values and evaluate

  SubstituteII

  V_1= 10π, V_2= 16/3π

  V_\text{solid}={\color{#FD9000}{10\pi}}+2 \left( {\color{#A800DD}{\dfrac{16}{3}\pi}} \right)

  MoveRightFacToNum

  a/c* b = a* b/c

  V_\text{solid}=10\pi+2\cdot\dfrac{16\pi}{3}

  MoveLeftFacToNum

  a*b/c= a* b/c

  V_\text{solid}=10\pi+\dfrac{32\pi}{3}

  NumberToFrac

  a = 3* a/3

  V_\text{solid}=\dfrac{3\cdot 10\pi}{3}+\dfrac{32\pi}{3}

  Multiply

  Multiply

  V_\text{solid}=\dfrac{30\pi}{3}+\dfrac{32\pi}{3}

  AddFrac

  Add fractions

  V_\text{solid}=\dfrac{62\pi}{3}

  MovePartNumRight

  a* b/c=a/c* b

  V_\text{solid}=\dfrac{62}{3}\pi
  We found that the volume of the composite solid is 623π cubic centimeters.

  Surface Area

  Now, we will find the surface area of the given composite solid. Notice that it is equal to the surface area of two hemispheres and the lateral area of the cylinder. Let's use the formulas for the surface area of a sphere and for the surface area of a cylinder.

  Surface	Hempishere	Lateral Area of Cylinder
  Radius	r= 2	r= 2
  Height	h= 2.5	-
  Area	A=1/2* 4π r^2	A=2π r h
  	A_1=1/2* 4π ( 2)^2= 8π	A_2=2π( 2)( 2.5)= 10π

  Now, let's find the surface area of the given solid.
  A_\text{solid}=2{\color{#FF0000}{A_1}}+{\color{#FD9000}{A_2}}

  SubstituteValues

  Substitute values

  A_\text{solid}=2\cdot{\color{#FF0000}{8\pi}}+{\color{#FD9000}{10\pi}}

  Multiply

  Multiply

  A_\text{solid}=16\pi+10\pi

  AddTerms

  Add terms

  A_\text{solid}=26\pi
  Therefore, the surface area of the composite solid is 26π square centimeters.