My answer o_O

My answer is 12.57 for the circ.

Since radius is half the diameter and the formula is c/d = pi, the equation should be written as C/4 = pi.

To find the c, I would need to inverse and write the solution as c = 4 x pi.

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Awesome job for doing the challenge!

@TK_F, great work attempting the challenge.
You’re answer is incorrect but that’s ok, we tend to learn better from our mistakes so let me try and unpack where you went wrong. :slight_smile:

You are correct that the radius is half of the diameter but if C/D = π then this means that C/2r = π, since you need to replace the diameter with 2x the radius so everything stays balanced. You could write this on one line as C/D = C/2r = π.

The challenge set a radius of 8 but I think you may have started with a diameter of 8 instead.
You’ve then halved that to get a radius of 4, which is ok for the problem you’re now working with.
However, by using C/4 = π you’re saying that the the diameter is 4 and the radius is 2 or C/4 = C/(2 x 2) = π.

With that in mind, give the challenge another go and see how you get on.
I’ve included the answer below so you can check your workings.

Start with a radius of 8, so;
r = 8 or d = 16.

From that you can either use;
C / D = π
C / 2r = π

These can then be rewritten as;
C = πD
C = 2πr

so your answer would be either:
C = π16
C = 2π8 = π16

In real-world decimal numbers, this equals about 50.27 (2 d.p.).

I hope this helps clarify things but if you’re still struggling please do reply to this thread and let me know.


Welp, I tried lol and went the wrong direction. Crap, you did say diameter is double the radius (2r). Unfortunately for me it was 4AM in the morning when I was attempting to solve this and wasn’t thinking straight. No excuses though!..better luck next time to me.

Well I’ll let you off it was 4am :wink:
It’s totally fine to make mistakes when you’re first learning - I even still make them now!
The main thing is to not be disheartened and to keep trying. With practice you can only get better :slight_smile:

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