The Estimation Jar Is So Much Fun

Last week, I reviewed a book entitled Messy Maths that encouraged parents and educators to get outside with their preschoolers. Here is a great idea from its pages.

Remember the estimation game? I’m sure you played a variation of it when you were young. There was probably a jar filled with jelly beans that you weren’t allowed to touch. You were given a slip of paper and asked to take a guess of how many jelly beans were in the jar. After everyone recorded their guess, the person who came closest to the actual number got to keep all the candy.

Here is a great way to do something similar with your kids that doesn’t require any candy.

“Create an estimation jar for the children to play with outside. The children fill it with objects of their choosing such as pebbles or cones. The group or a child has to estimate how many objects are in the jar before counting them.”

You can use any clear container you have at home. Plastic peanut butter jars and cake sprinkle containers work great.

“When the children are filling containers such as milk bottles or transparent tubes with stones or gravel, this is an opportunity for them to estimate and count. Challenge the child or group to release half the amount of stones and count them. This can then become the basis for estimating the amount of stones left in the bottle. These can then be removed and counted.”

You can do this activity at the park with little stones or the wood chips they use to line the bottom of the playground structure. You can even try it at the beach.

“The group needs a plastic bottle or a transparent container. Any interesting things they find can be put into the bottle, such as little bits of driftwood or shells. Next, the children should half-fill their bottle with dry sand and put the top back on. They can then have fun estimating what is inside the bottle and in what quantity (e.g. three shells, two pebbles, five pieces of sea glass and one driftwood stick).”

Here’s an activity I’ve done as a teacher. It proves something known as the Law of Large Numbers. It is an amazing piece of mathematics trivia. And it works most of the time. If you have a large group playing the jelly bean game, add all of the guesses together and divide that by the number of participants. For example if 25 people made estimations totaling 2800, 2800 divided by 25 = 112. There were likely close to, or exactly, that many candies in the jar. Try it.

This is a fun twist on the estimation jar and kids will love it!