Why is 22/7 used to find the circumference & area of a circle??

Question

It could also be 3.14

I know pi is the ratio between the circumference to a diameter of a circle, but why is it used to calculate the area of a circle??

Answer 1

That number (pi) is the ratio of any cicle's circumference to its diameter, no matter how big or small it is.

Answer 2

Pi is first defined as the ratio of the circumference to the diameter, so of course it comes into the formula for the circumference.

You would not think at first that there was any good reason why the same constant should come into the formula for the area. It could quite well have turned out to be a different constant.

But when you slice up the circle into many many very thin triangles, its area is the sum of all the triangles, and each triangle has an area defined by the whole radius and a tiny bit of the circumference. So the area depends quite simply on the circumference, which means that it has to involve the same constant after all, not a different one.

Answer 3

It's a close approximation of pi. When I was younger I was always forgetting pi. and used 22/7 a lot. Why I could remember 22/7 and not pi I still don't know but as a memory tool it worked for me.

Answer 4

22/7 is a decent approximation for pi. A better one is 355/113, but it may be harder to use in math problems. The real advantage to 22/7 is that it is easy to develop math problems where the radius is a factor of 7 so that the math is easy.

Answer 5

It's the best approximation to pi that can be expressed as the ratio of two reasonable sized numbers. Exact pi is irrational (it has an infinite number of digits after the decimal point).

Answer 6

i have no idea why all i know i that 22/7 is eqal to pi

Answer 7

Ermmmm

Because that's the figure that gives the correct result