Find The Volume - Blog Posts

As a repeated jellybean counting contest winner, I wanted to share with you all my secret so that you can win prizes too this holiday season.

As a young child and adult, I have used this method and won each time. You can guess the volume in this odd unit using these steps.

Identify the shape of the jar. Is it a cube, rectangular prism or a cylinder?

What I'm describing below is for a cylinder, the most common jar shape.

First, obtain RADIUS: If you are allowed to touch and pick up the jellybean jar, you can count jellybeans in a straight line across the bottom of the jar. If you are disallowed from touching the container, just count across the the top in a straight line. The full line across of this circle is known as the diameter. Half the line across is known as the radius. You can count all the way across and then divide in half. You may be cutting the jellybean in half and get a decimal when you do this. No problem.

Second, count your HEIGHT: This is the easy step. You just count the front face of the container. Count jellybeans in a straight line up the side of the jar. This is your height.

Plug and calculate: For a cylinder jar, your volume can be found by calculating 3.14 x RADIUS² x HEIGHT.

So multiply your radius first since PEMDAS tells us the exponent needs dealt with first. Squaring a number is just that number multiplied by itself. After you have that, multiply by pi and by the jellybean height.

The answer you get could be a fraction or decimal. More than likely, the person who put the jellybeans in the jar did not include halved beans. So round up your number if it ends in .5 or higher. And round down to the nearest whole number if it ends in .4 or lower.

**If you have a complex jar shape, mentally cut the jar where the shapes change! Then calculate using the different volume formulas.

I hope this helps someone win a gift card or impress someone at a Christmas party!