smartread345
smartread345 smartread345
  • 23-01-2015
  • Mathematics
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If the length of the radius of the circle is doubled, how does that affect the circumference and area. Explain please.

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naǫ
naǫ naǫ
  • 24-01-2015
radius - r
area:
[tex]A_1=\pi r^2[/tex]
circumference:
[tex]C_1=2 \pi r[/tex]

the length of the radius is doubled
radius - 2r
area:
[tex]A_2=\pi \times (2r)^2=\pi \times 4r^2=4 \pi r^2[/tex]
circumference:
[tex]C_2=2 \pi \times 2r=4 \pi r[/tex]

[tex]\frac{A_2}{A_1}=\frac{4 \pi r^2}{\pi r^2}=4 \\ \\ \frac{C_2}{C_1}=\frac{4 \pi r}{2 \pi r}=\frac{4}{2}=2[/tex]

When the length of the radius is doubled, the area is quadrupled and the circumference is doubled.
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