Question

What is the circumference of a circle with a radius = 4.25 in? What is the circumference of a circle with a diameter = 27.8 m?

Answer 1

The first circumference is 26.69 and the second is 87.292

Explanation:

The formula for finding the circumference of a circle is `2pir`
Think about it this way: Multiply 2 `xx` radius of the circle `xx` `pi` (which is always going to be `3.14`).
The first question tells you the radius, so we already know that `r = 4.25` All we have to do now is plug that into our equation.

`(2 xx 3.14) xx 4.25` (now multiply `2` and `3.14` together)
`6.28 xx 4.25 = 26.69` (now multiply `6.28` and `4.25` together)
There's your first answer!

The second one is a little more complicated, but still fairly straightforward. The radius of a circle is always half of the diameter , so divide `27.8/2 = 13.9`. Now we know `r = 13.9`. Let's plug that in.
`(2 xx 3.14) xx 13.9` (now multiply `2` and `3.14` together)
`6.28 xx 13.9 = 87.292` (now multiply `6.28` and `13.9` together)
There's your second answer!