Grade 4 - Progress in Mathematics

Estimation

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Sometimes it is inconvenient, difficult,

or even impossible to report the exact

number of items in a group or set.

When you cannot report an exact number,

you can use an estimate. An estimate can be

a rounded number that tells abouthow much

or abouthow many.

Here are some examples of estimates:

• So far, 1,000,000 different species of
  insects have been discovered.


• One hundred years ago the worldwide
  population of tigers was 100,000. Today the
  number of tigers is 7000.


• The age of the oldest bird on record, a cockatoo,
  was 80 years. It was fully grown when captured
  in 1902 and died in the London Zoo in 1982.

Discuss these questions with your group:

1. For each example, why is each number
   reported as an estimate, or rounded
   number, rather than an exact number?


2. How are all the estimated numbers
   alike? How are they different?


3. Read the examples again. Do you think
   estimating is the same as guessing?
   Why or why not?

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