1)find diameter, radius and area of circle when circumference is 78.5 cm.
2)find diameter, radius and circumference of circle when area is 78.5 cm^2.
answer these with explanation please.
Answers
Answer:
Step-by-step explanation:
1)find diameter, radius and area of circle when circumference is 78.5 cm.
For radius
formula of a circumference is 2πr
r is radius
π is 22/7 or 3.142
we have to rearrange the formula to get the radius
2πr =circumference
r =circumference/2π
The circumference is 78.5 cm so we have to substitute it into the formula above (r =circumference/2π)
r = 78.5 cm /2π
r = 78.5 cm /2 * 3.142
r = 78.5 cm /6.284
r = 12.49204
r = 12.492 cm
For diameter
formula for diameter is 2( r )
The radius is 12.492 so we have to substitute it into the formula
diameter = 2( 12.492 )
diameter = 2 * 12.492
diameter = 24.984 cm
Now for the area
the area of a circle is π r^2
r is 12.492 cm
area = 3.142 * 12.492^2
area = 3.142 * 156.05
area = 490.3091
area = 490.309 cm
2)find diameter, radius and circumference of circle when area is 78.5 cm^2.
For the radius
the area of a circle is π r^2
we have to rearrange the formula to get the radius
π r^2 = area
r = √area/ π
Then we substitute 78.5cm into the formula
r = √78.5/ π
r = √78.5/ 3.142
r = √24.984
r = 4.998 cm
For the diameter
formula for a diameter is 2( r )
The radius is 4.998 cm so we have to substitute it into the formula
diameter = 2( 4.998 cm)
diameter = 2 * 4.998 cm
diameter = 9.996 cm
Now for the circumference
formula of a circumference is 2πr
circumference = 2 * π * r
circumference = 2 * 3.142 * 4.998 cm
circumference = 31.407432
circumference = 31.407 cm
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