Transcript Surface Area of a Cylinder - Western Reserve Public Media

of
Cylinders
Surface Area
• What does it mean to you?
• Does it have anything to do with what is in
the inside of the prism?
VOLUME (not surface area) is the
amount a shape can hold inside.
• Surface area is found by finding the area of
the circle and the area around the cylinder
and adding it together.
Surface Area
of Cylinders
• What is area?
The amount of square units that will
COVER a shape.
• How will the answer be labeled?
Units2 because it is area!
SURFACE AREA of a CYLINDER.
Imagine that you
can open up a
cylinder like so
You can see
that the surface
is made up of
two circles and
a rectangle.
The length of the rectangle is the
same as the circumference of the
circle!
EXAMPLE: Round to the nearest TENTH.
Top or bottom circle
Rectangle
A = πr²
C = length
The length is the
same as the
Circumference
A = π(3.1)²
A = π(9.61)
A = 30.2 cm²
Now add:
30.2 + 30.2 + 234 =
SA = 294.4 in²
C=πd
C = π(6.2)
C = 19.5 cm
Now the area
A = lw
A = 19.5(12)
A = 234 cm²
This could be written a different way.
2πr = πd
So this formula could be
written:
SA = 2πr² + πd ·h
A = πr² (one circle)
This is the area of
the top and the
bottom circles.
There is also a formula to find surface area of a
cylinder.
Some people find this way easier:
SA = 2πrh + 2πr²
SA = 2π(3.1)(12) + 2π(3.1)²
SA = 2π (37.2) + 2π(9.61)
SA = π(74.4) + π(19.2)
SA = 233.7 + 60.4
SA = 294.1 in²
The answers are REALLY close, but not exactly the
same. That’s because we rounded in the problem.
Now It’s YOUR Turn!
I think I can!
I think I can!
I think I can!
I think I can!
I think I can!
I think I can!