#2569. Estimation Using Goldfish Crackers

Mathematics, level: Elementary
Posted Fri May 3 13:39:10 PDT 2002 by RaeJean A. Brown (raejean@paulbunyan.net).
Student, Bemidji, USA
Activity Time: 30-35 Mins.
Concepts Taught: Estimation and Rounding

Please Note: If you use my lesson plan, please give me the credit, I did this all by myself.
ฉ RaeJean Brown 2002

Grade Level: 2nd grade Area 4A Number Sense. A student shall use number relationships to represent information and solve problems by: (1)... (2).... (3) solving problems and justifying thinking by selecting appropriate numbers and
representations; using operations, patterns, and estimation; generating multiple solutions; organizing data using pictures and charts; and using concrete objects, diagrams, or maps to solve simple problems involving counting, arrangements, or routes.

Concept: Estimation and Rounding

Objective(s):
• Students will be able to solve problems by estimating and rounding numbers.
• Students will be able to pick numbers within reason to represent certain objects.

Materials:
• Small goldfish bowl
• Goldfish crackers
• Copy of the estimation song
• Individual snack bags with 10 goldfish
• Review Worksheets

Procedure:
• First I will explain that we are doing a unit on estimation and rounding.

• I will hold up the fish bowl and ask them if they can guess how many goldfish crackers are in there. I will call on students and hear their guesses.

• I will hand out the copy of the estimation song (the snack bag will be stapled with it). I will say, seeing that there are 10 goldfish in the bag, how many bags of goldfish will fill
up the fish bowl.

• I will introduce the estimation song and have us sing it all the way through. Then I will tell them how many gold fish are actually in the bowl.

• We will also discuss how estimation can be used in other ways other than just guessing how many objects there are, we can use it in math for addition and subtraction as well as other operations. This is where rounding comes in. I will show some examples.

Example: 26 + 12 = ? (30 + 10)
If the last digit in the number we are working with is 5 or greater, we are going to round up. So 26 would become 30 (the tenths place will also have to change to a greater number so it does not become 20). If the last digit in the number we are working with is below 5, we will round down. 12 will become 10. Now that we are doing the math, we will say 30 + 10 = 40. That will be our estimate answer by rounding.

Another example is: 41- 23 = ? (40-20)
By applying what we just learned about rounding, 41 would be rounded down to 40 and 23 will also be rounded down, but to 20. Then we get 40-20 and we know this is 20. This isn't the
"correct" answer. But it is right in terms of estimating.

Evaluation: I will see if the students are grasping the concept of rounding and estimating by giving them a worksheet that has math problems that they can estimate. I will also ask if they know anything else that can be used in estimation (such as time, measurement, area). And we can focus on that later in the unit.

---

The Song:
Estimate*

1. we estimate (we estimate)
so we can know (so we can know)
how many things (how many things)
there are to show (there are to show)
we estimate so we can know, how many things there are to show

2. we can round up (we can round up)
we can round down (we can round down)
just do the math (just do the math)
what have we found (what have we found)
we can round up, we can round down, just do the math, what have we found

3. it's fun to guess (it's fun to guess)
so we can know (so we can know)
how many fish (how many fish)
are in that bowl (are in that bowl)
it's fun to guess, so we can know, how many fish are in that bowl

4. now don't you fret (now don't you fret)
and don't you frown (and don't you frown)
the answer you get (the answer you get)
is never wrong (is never wrong)
now don't you fret and don't you frown, the answer you get, is never wrong

5. if all of math (if all of math)
was just this fun (was just this fun)
well boy oh boy (well boy oh boy)
what we'd get done! (what we'd get done!)
if all of math was just this fun, well boy oh boy what we'd get done!

6. that's all there is (that's all there is)
there is no more (there is no more)
until we work (until we work)
on unit four (on unit four)
that's all there is, there is no more, until we work, on unit four.

*"Estimate" is to the tune of the song, "The Bear" which can be found on pp. 38-39 in the Wee
Sing Fun 'N' Folk book by Pamela Conn Beall and Susan Hagen Nipp.1989.