Estimation is easy!

Anyone who has had me as a teacher in Grade 6 or 7 has heard me echo, “Estimation is Easy!”…but is it?! Estimation can be a difficult skill to learn because it involves number sense, spatial sense, measurement sense and lots of mental computation. This important skill is often left out of the curriculum, or is inserted as an insignificant add-on because approximate answers are not valued as much as correct answers; but they should be!

that was easy

That was easy!

Why is it important?

Estimation may not be easy, but it is essential! We use estimation every day, whether estimating how much sand to buy to fill the new sandbox, or guessing whether our suitcase is overweight, or figuring out if we have enough money to buy something. Estimation helps develop number sense and fluency and is a great way to get children to visualize amounts mentally.

“The emphasis on learning in math must always be on thinking, reasoning and making sense.” Marilyn Burns

And what better way to emphasize these skills than to begin problems with estimation!

What does it accomplish?

Mathematicians agree on these four things:

  1. It helps children focus on the attribute being measured (length, time, volume etc.)
  2. It provides intrinsic motivation for measurement because children want to see how close their guesses are.
  3. It helps develop familiarity with standard units, if that is what is being used to estimate.
  4. It develops referents or benchmarks for important units and as a result, lays the groundwork for multiplication.

When should you start?

My belief is that once your child can count with meaning and he or she can comprehend the language of comparison (more, less, the same), you can start estimating with small amounts. Why not start when the kiddos are small and not yet pre-programmed to believe that right answers are more valued than close answers?

That being said, Rosalind Charlesworth suggests that children can’t make rational estimates until they have entered the concrete operations stage (ages 7-11 yr). This is because she believes children should have already developed number, spatial and measurement sense before they can make educated guesses.

Well, let’s see what Rory thinks; will he make a wild guess or a rational estimation? He’s 4 1/2 years old and in the pre-operational stage of development, but I believe he can make good estimates through motivating activities, coupled with appropriate phrasing of questions.  Let’s see how he does.

The Problem

We are going to our new house on the weekend to measure the rooms so we can plan where to put our furniture, but oh-oh…Daddy forgot the measuring tape! What could we use to measure instead? Oliver! And he is a very willing helper…at least in the beginning!

As you can see from Rory’s first attempt, he made a rational estimate even though his estimate wasn’t that close. He thought it would take 10 Olivers to line the wall, but it only took 5.  I knew his guess was rational because he explained it to me and it made sense. His mistake was that he counted 10 steps initially, instead of 10 Olivers.

Notice how he has already improved his understanding and his next estimate was much closer; he guessed it would take 1 Daddy and it actually took 2. I give him a thumbs-up for his first estimate activity and look forward to doing more with him to see how he improves.

Teaching Tips

Here are some tips so your pre-school children meet with success also:

To start, provide numbers for the children to choose from so they don’t have to pull numbers out of thin air.
Stick with numbers they can count up to.
Begin using benchmarks (5 and 10).
Use and teach proper words: about, around, estimate.
Ask good questions that encourage comparisons:

·         Will it be longer, shorter or the same as _____________?

·         Will it be more or less than ____________?

·         Will it be closer to 5 or 10?

Ask good questions to ensure understanding:

·         How did you come up with your estimate?

·         How can we find out whether your estimate is reasonable?

Start with length, weight, and time.
Let the estimate stand on its own; do not always follow with the measurement.
Develop the idea that all measurements are approximations (thus estimates!), the smaller the units – the more precise but still approximate.
Incorporate estimation activities into your every-day life so it becomes second nature.

It is easy to incorporate estimation activities into your daily life and the more your child practices, the better they will become! Need help getting started?

Click here for activities!

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