Tag: Diameter

Diameter?

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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!

How big is Earth

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My Earth painting.

How big is Earth’s diameter? Just under 8,000 miles. How big is its circumference? Just under 25,000 miles. That’s not very big really. There are statistics saying how many Earth’s fit into Jupiter, the biggest planet in the Solar System, or even how many Earth’s would fit into the size of the Sun.

What I’m trying to say is, this is the third planet from the Sun, in the habitable region of the system (not too hot or too cold) and we need to look after it. We are using up its resources at an alarming rate, polluting our home world with plastics and toxic waste, killing off the insects including bees with insecticides and heating it up till the North and South polar icecaps are severely effected and melting rapidly. Why are we doing this? Are we, like Covid19, like a virus, impacting on our host, the Earth.

Discuss…….