# Diameter?

How do you work out the radius of a satellite dish when all you know is its diameter? That was the strange question I tried to answer on twitter last night.

First of all I had to remember my school girl maths from fifty years ago.

I remembered the diameter if found with the formula 2 pi r. Where pi is 22/7. I couldn’t remember the decimal version and I wasn’t using a calculator so I divided 7 into 22 and got 3.142. Then r is the radius, which is half of 70=35.

So then I had to multiply (on paper again) 2 Xx 3.142= 6.284. And multiply that by 35. As my multiplication is not good I added 3 lots of 62.84 together = 188.52, then added 6.284 together five times = 31.41 (yes it’s long winded but accurate). Add the two figures together and you get 219.93.

I don’t know BODMAS or PODMAS or whatever they are called. But I actually got it right. Not to bad for an oldie!

PS the formula for area is pi r squared. Not going there!

## 2 thoughts on “Diameter?”

This site uses Akismet to reduce spam. Learn how your comment data is processed.