© 2004  Rasmus ehf

Rounded numbers (Approximation)

Print

Lesson 1.

=  means "the same as" or "is equal to".

   means "about the same as" or "approximately".

Rounding to the nearest ten

Let's look at the number line. We see that the number 24 is closer to 20 than to 30. 

24  20

Rounding to the nearest ten

Here we see that the number 27 is closer to 30 than to 20.

27  30

Rounding to the nearest ten

Here we cannot see if 25 is closer to 20 than to 30. 

25  30

Rules for rounding numbers.

If the digit following the rounding place ends in 0, 1, 2, 3, or 4, we round down. 

                    24  20   Round down

If the digit following the rounding place ends in 5, 6, 7, 8, or 9, we round up. 

                    25 30   Round up

Review the place values:

Decimal places come after the decimal point.    (to the right of the decimal point)

Example 1:  

Round 348.537  to the nearest hundred.	When 0, 1, 2, 3 or 4 come after the rounding place we, round down.
348.537    300

Example 2: 

Example 3:

Example 4:

Example 5:

Practice these methods and then try Quiz 1 on Rounding numbers.
P.S. Remember to fill in your Check list as you go through the exercises and quizzes.