Transcript Circles - bYTEBoss

Circles
How do you find the circumference,
radius, and diameter of a circle?
What is a circle?
• A circle is a plane
figure that is curved.
• Circles do NOT have
sides or angles.
Where do you see circles in our
classroom?
Write these down in your math
notebook.
What is circumference?
• Circumference is the distance
around a circle.
• How can you find the
circumference of your Oreo cookie
using a piece of yarn and a ruler?
What is the diameter of a circle?
• The diameter of a
circle is the distance
across a circle.
diameter
• If you walked from
one side of a circle to
the other side, you
would be walking the
diameter of the circle.
• Can you find the
diameter of your Oreo
cookie?
What is the radius of a circle?
• The radius of a circle is
half of the diameter.
• If you walked halfway
across a circle, you would
be walking the radius of
the circle.
• Can you find the radius of
your Oreo cookie?
radius
How do you find the radius of a
circle if you know the diameter?
• You can find the radius of a circle if you
know the diameter of the circle by dividing
the diameter in half.
• Can anyone think of an easy way to divide a
number in half? Is there a number we use
to divide other numbers in half?
Find the Radius
• Can you find the
radius of this circle?
• You know that the
diameter is 10cm.
• You can divide 10cm
in half to find the
radius.
• 10cm ÷ 2 = 5cm
Diameter = 10cm
Try It Out!!!
• Do you know the
diameter of the circle?
diameter= 12cm
• How can you find the
radius?
• What operation should
you use?
Is this how you solved the
problem?
• You can find the
radius of this circle by
dividing the diameter
in half, or by 2.
• 12cm ÷ 2= 6cm
• The radius of the
circle is 6cm.
How can the diameter be found if
the radius is given?
• If the radius is given, you
can double the radius to
find the diameter.
radius= 4cm
• Find the diameter of this
circle by doubling the
radius that is given.
• 4cm x 2= 8cm
• The diameter of this circle
is 8cm.
Try This Out!!!
• Do you know the
diameter of the circle?
• How can you find the
diameter?
• Which operation
should you use?
radius= 6in.
Is this how you solved the problem?
• You can find the
diameter of the circle
by adding the radius
two times or by
multiplying the radius
by 2.
6cm + 6cm= 12cm
Or
6cm x 2= 12cm
Practice
Find the radius of each
circle using the diameter
that is given.
1.
2.
3.
4.
Diameter= 24cm
Diameter= 18in.
Diameter= 36mm
Diameter = 14in.
Find the diameter of
each circle using the
radius that is given.
1.
2.
3.
4.
Radius= 7in.
Radius= 9cm
Radius= 23mm
Radius= 52cm