© Feb. 2003  Rasmus.is

Rounded numbers (Approximation)

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 30. 

24  20

Rounding to the nearest ten

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

27  30

Rounding to the nearest ten

Here we cannot see whether 25 is closer to 20 or to 30. 

25  30

Rules for rounding numbers.

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

                    24  20   Round down

If the digit following the rounding place  is  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 Rounded numbers.
P.S. Remember to fill in your Check list as you go through the exercises and quizzes.