Estimation
3rd Grade
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Look at the overhead
Estimate how many paper clips your
teacher placed on the overhead.
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Party Time
• Its your birthday next week. You
sent out 25 invitations, but not
everybody has told you if they were
coming. You go ahead and just
estimate that 20 people will show up.
• What problems may you run in to?
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Add the following
50 + 25 + 25 + 50=
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What is the difference?
• Estimation: is a guess of the
approximate size or amount
• Approximate: nearly exact, to be
almost the same as or very close to
• Exact answers: the correct answer
used by adding, subtracting,
multiplying, or dividing numbers
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When should I Estimate?
• Shopping
• Time it takes to get somewhere
• Measurements
• When you want to find an
approximate answer
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When do I want an
EXACT number
• Documents
• Birthdays
• Change received
• Recipes
• Medicines
• Race Times
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Finding a solution
• Whether you ESTIMATE or find an
EXACT answer, you still need to find
the answer using mental math, a
calculator, or paper/pencil.
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Use your cards to answer
Exact or Approximate?
You decide
• You pay for your meal at McDonalds.
Is the change you get back from the
$5.00 Exact or Approximate?
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3-2-1 show me…
Exact
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Exact or Approximate?
You decide…
• You get a prescription from the
Doctor when you were sick. Is the
medicine you take an exact amount or
an approximate amount?
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3-2-1 show me…
Exact
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You decide…
• Your Mom gives you money for the
movies and a snack. Do you know
what you will spend exactly or do you
have an approximate?
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3-2-1 show me…
Approximate
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You decide…
• You have a tree that is about 10 feet
tall outside your house. Using that
tree, would you find out exactly how
tall your house is or approximately
how tall your house is?
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3-2-1 show me…
Approximate
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What tools can I use for
estimating?
• Use what you know for measuring.
• Use a sample
• Use reasonable answers
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Use what you know
• What is the measurement of the
doorknob? Think: I am almost 4
feet tall. The knob is lower than me,
so it is about 3 feet high.
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Use what you know…
• If you are 4 feet tall. And you were
to lay down. You are about the
length of 2 desks. How many desks
would it take to measure the length
of the room?
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Get a sample
• Its estimation jar again this week.
Here are all the gummy bears dumped
out. Sort out 10. Knowing these are
10, what is the approximate number
of all of the bears in the jar.
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Here are 10
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Can you estimate
the bears?
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Actual number of
bears is 54
Stand up if you were over
54
Stay sitting if you were
under 54.
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Get a sample
• Lets try again with flies. Here are 10
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Now estimate how many flies
here…
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48 flies
• Stand up if you estimated more than
48?
• Stay sitting if you estimated less
than 48?
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Over or Under
• Overestimate: happens when you
estimate too high or great. The
estimate is greater than the exact
number.
• Underestimate: an estimate less
than the actual answer.
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Lets practice
• Use your practice sheet to determine
when to estimate and when to find an
exact amount.
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Day 2
Reasonable Estimate
• My chair is about 2 feet tall
• I need to take about 10 dollars to
the movies for the ticket and a drink.
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Unreasonable Estimate
• Our mailbox is about 10 feet tall
• If I buy one meal at McDonald’s, my
mom needs to give me $20.00.
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Reasonable or
Unreasonable
• There are about 180 3rd graders in
our school.
Reasonable or Unreasonable
• A duck weighs about 50 pounds
Reasonable or Unreasonable
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Reasonable or
Unreasonable
• The elevator holds about 8 people.
Reasonable or Unreasonable
• You give your dog about 3 cups of
water a day.
Reasonable or Unreasonable
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Lets try some estimates…
• Use your recording sheet for the
following:
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Don’t forget to tell if you over
or underestimated
• Estimate how many jumping jacks you can
do in a minute.
• Estimate how many people have on shoes
that tie today.
• Estimate how many pockets you have on
your clothes.
• Estimate the amount of candy in the bag.
• Estimate how many paper clips are in a full
box of small paper clips.
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