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How to Guess the Amount of Jelly Beans in a Jar

As the word "guess" implies, there's no foolproof method to guess the amount of jelly beans in a jar. Generally it seems that the prize in such contests goes not to anyone with a strategy, but to someone who just pulled a number out of thin air. However, there is a mathematical method that should get you at least into the ballpark of the actual number of jelly beans in a jar.

Instructions

- 1
  Count the number of jelly beans around the outside of the bottom of the jar. Start with a bean that sticks out from the ones around it, or put your finger somewhere to keep track. Try to count the number of beans in just a single layer, as accurately as you are able. This number can be considered to be the circumference of the jar, measured in bean units.
- 2
  Use the formula for finding a circle's circumference to find the circle's radius in bean units. This formula is circumference = 2 x pi (approximately 3.14) times the radius. By rounding pi off slightly more, we can approximate the formula as circumference = radius x 6, or in other words, radius = circumference / 5. In other words, dividing the circumference number by six should give you an approximate measurement for the radius. So, for example, if there are 30 jelly beans around the outside of the bottom of the jar, divide this number by 5 to get a radius measurement of 6.
- 3
  Find the area of the bottom of the jar in bean units. The formula for finding the area of a circle is area = pi (about 3.14) times the squared radius. So, multiply the radius number by itself, and, to get a rough estimate, multiply this number by 3. For example, with a radius of six, your formula would be six squared (six times six, or thirty six) times three, which equals 108. According to this formula, a single layer of jelly beans in the jar should be about 108 beans.
- 4
  Count how many layers of beans are in the jar. Starting with a single bean at the bottom of the jar, count the number of beans in a single line towards the top. This number is the height of the jar of jelly beans, measured in bean units.
- 5
  Use the formula for volume of a cylinder to guess the amount of jelly beans in a jar. This formula is volume = area of the base x height. So, multiply the area number you found using the last formula by the bean height. For example, multiply the base of 108 beans by a height of, say, 10 beans, for a result of 1080 total beans in the jar.

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