A park has a circular goldfish pond. What is A, the approximate area of the surface of the pond, if it's radius is 5 feet?

Question

I need help 

Answer 1

The area of a circle is Pi  times radius², and with the radius of the circular pond being 5 feet, the answer is 3.14 x 5² = 78.5 ft²

Answer 2

Hi, the area of any circle whose radius is "r" is given by the formula "pi * r * r" where the * means multiplication and where the Greek letter pi stands for the mathematical constant which is on your calculator and which is roughly 3.14159265....

We often write "r^2" instead of "r * r" where "r^2" is read out loud as "r-squared" but I'll use "r times r" notation below.

Since the digits of pi continue forever, you will need to round your answer. So it depends on how accurate an answer the problem is requesting. Often 3.1416 is good enough (we get this by rounding "3.14159265...." to the nearest fourth decimal place. And sometimes even "3.14" is good enough. So check if the problem asks how many digits it wants in the answer, that is, how accurate it wants us to be.

On your calculator there is probably a "pi" symbol if you know what the Greek letter looks like (kind of like a house with two walls and a roof)...so you can type "5*5*pi" on your calculator. Otherwise try "5*5*3.1416" for a decent approximation, you'll get: 78.54 which is more accurate than the "78.5" you'd get by using only "3.14" for pi.

Bonus: Googlehas a built-in calculator right in the search engine so you just need to type "5*5*pi" and it will give you an even more accurate answer (try it!) it gave me:

78.5398163397

which you can round to fewer digits; to as many digits as are needed/requested by the problem (or if the teacher of the class told the students to only show up to 4 digits for example)