How Do You Guess How Many Jelly Beans Are in a Jar?

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Two main methods are used to estimate the number of jelly beans in a jar, including mathematical formulas for volume and statistical estimation by counting the number of candies in a similar jar. An easy way to estimate the beans is to count the height and diameter of the jar in beans, and then input those numbers into a volume calculation for round cylinders.

The volume formula for a cylinder is V = pi x r^2 x h. One suggestion for using this formula involves rounding pi to 3 and counting the radius as half of the jar’s diameter in beans. For example, if a jar is 10 beans in diameter and 20 beans in height, the volume is three times 5 squared times 20, or 3 times 25 times 20. The answer is approximately 1,500 beans.

Estimate the number of jelly beans by taking statistical samples. Obtain the exact same jar with jelly beans of the same size. Count jelly beans into the jar, up to the exact level of jelly beans, several times to get an average. For instance, it could be that over six different counts there are 587, 579, 593, 579, 591 and 585 jelly beans. This averages out to an estimate of 586 jelly beans in the jar.