Question

1.2.12 m18 inC3.4.35 km5.6.15.6 cm7 mm

Answer 1

The required solution is the circumference of the circle for the given radius or diameter

The formula for the circumference of a circle with radius r is :

`C\text{ = 2 }\pi\text{ r}`

The formula for the circumference of a circle with diameter d is:

`C\text{ = }\pi\text{ d}`

For the first circle with a radius of 12m:

`\text{Circumference = 2}*\text{ }\pi\text{ }*\text{ 12 = 24}\pi`

For the second circle with a diameter of 18in :

`C\text{ = }\pi\text{ }*\text{ 18 = 18}\pi`

For the third circle with a radius of 2.8ft:

`\begin{gathered} C\text{ = 2 }*\text{ }\pi*\text{ 2.8 } \\ =\text{ 5.6}\pi \end{gathered}`

For the fourth circle with a diameter of 35km:

`\begin{gathered} C\text{ = }\pi\text{ d} \\ =\text{ }\pi\text{ }*\text{ 35 = 35}\pi \end{gathered}`

For the fifth circle with a radius of 7mm:

`\begin{gathered} C\text{ = 2 }*\pi*\text{ r} \\ =\text{ 2 }*\text{ }\pi\text{ }*\text{ 7} \\ =\text{ 14}\pi \end{gathered}`

For the sixth circle with a radius of 15.6 cm:

`\begin{gathered} C\text{ = 2}\pi r \\ =\text{ 2 }*\text{ }\pi\text{ }*\text{ 15.6 } \\ =\text{ 31.2 }\pi \end{gathered}`

Note: Circumference has a unit. It's unit depends on the unit of the radius/ diameter