## Saturday, November 7, 2015

### Number Sense and Estimation

Since the very beginning days of school this year, our overarching theme in math has been "number sense".  Number sense refers to a student's "fluidity and flexibility with numbers," (Gersten & Chard, 2001). Children at this age are beginning to have sense of what numbers mean - how a 9 in the thousands place represents 9000, for example. They are learning numbers' relationship to one another, and can use numbers in real life situations. We spend a lot of time playing with numbers, and doing mental math. Strategies of coming up with answers in many different ways are encouraged and shared with each other. I'm always asking, "What did your brain do to come up with that answer?" "Can someone come up with a different way?"

Number sense is incredibly important. I want children to be as comfortable with numbers as they are with words. Outcomes should be sensible and expected. Sometimes when I am working one-on-one with a student, we will read story problems together, and then talk about the answer they gave, and whether it "makes sense". Often children do not go to this step independently at first, but asking that simple question often shows them that something went wrong somewhere.

Estimation is an integral part of number sense and computation. In fact, you could say that most of the math we do every day relies on both mental math and estimation. I gave the example of being in the store with \$100.00 to spend - you don't want to get up to the counter with \$500.00 worth of items because you couldn't estimate how much everything costs. You need to estimate how much paint you will need when it is time to redecorate, how much tip to leave when dining out, what time to leave for school when you know there is construction.

This week, we are doing a fun little estimating game at the beginning and end of math class. I fill a clear container with various objects. Children write down their estimates on a piece of paper, after talking about various strategies they could use. We got a lot of ideas from a math book called, "Betcha!"

First and foremost, we ask ourselves, "Is our guess reasonable? Does it make sense?

After workbook time, we count the pieces. We do this quickly by using the base 10 system, our old friend. Using 10 paper plates, children speedily group 10 pieces onto each plate. We can see at a glance how many we actually had.

I told my students that several years ago, I actually won a contest at Cherry Republic. They had a HUGE jar filled with chocolate covered cherries, and I was the closest to figuring out the total number. Just yesterday I went to lunch at Noodles, and what did I see? This!

Perhaps your estimators could take a little trip to Noodles and practice their skills. Who knows? You may just win a big plate of pasta!