Question

Find the radius of a circle whose circumference is 31.4 centimeters.

Answer 1

Hey there! :)
So we have a formula that relates Circumference to the Radius of a circle.

Answer 2

?

Answer 3

\[\Large\rm \color{orangered}{C}=2\pi r\]Let's rewrite our pi as 3.14 so it's easier to work with:\[\Large\rm \color{orangered}{C}=2\cdot 3.14 r\]Multiplying the 2 and 3.14 together gives us:\[\Large\rm \color{orangered}{C}=6.28 r\]And they told us that the circumference of this particular circle is \(\Large\rm \color{orangered}{31.4}\).

Answer 4

So our equation is:\[\Large\rm \color{orangered}{31.4}=6.28 r\]From here we need to solve for r,
understand how to do that?

Answer 5

Find the area of a circle whose circumference is 31.4 centimeters. So you do 3.14 times 31.4

Answer 6

No.
We've simplified our equation to 31.4 = 6.28r

See how 6.28 is `multiplying` the r?
To isolate the r, we do the inverse of `multiplication`.
So we'll divide each side by 6.28.

Answer 7

So then you turn to your trusty calculator to finish things up for you.
r = 31.4 / 6.28

Answer 8

1.Find the radius of a circle whose circumference is 31.4 centimeters. =6.28


Find the area of a circle whose circumference is 31.4 centimeters =5

Answer 9

2. Find the area of a circle whose circumference is 31.4 centimeters =5

Answer 10

Hmmm no :(
If you followed my instructions, you should get that the radial value is `r=5`.
The question after that uses this information to calculate area.

So our r=5

Our formula for area is A=3.14 r^2

So plug in the r value that found in the first question.
A=3.14 (5)^2

and simplify.

Answer 11

I'm very confused so number 1 is. 5

Answer 12

yes

Answer 13

Then what would number 2 be