Rounding and Estimation

Rounding: Replace one number with another number ?that tells about how much or how many



Round down when it's 4 or less (let it rest)
Round up when it's 5 or more (raise one more)

Here's where to start: Find the digit in the rounding place.
        Example: Round to the nearest ten
                          758
     *8 is more than 5 so we will round the 5 up one more to 6 and turn the other digits to the right to zeros....
                  760 is our rounded number!

*Round to the nearest ten thousand: 1,453,544 ........round to 1,450,000

* Do the same thing for decimals!
   *Round to the nearest tenth:  0.432 (3 is less than 4 so we'll let it rest and become 0.400)

**Rounding with addition:

459+528

Round each number to the same place value

*Let's do the 100's place

500+500

The sum is about 1,000

**Front End Estimation:

369-128

Subtract only the front-end digits and change the other digits to zeros


300 - 100

The difference is about 200

**Clustering 


369+398+403+389+212+410

Five numbers can all be "clustered" or  rounded  to 400. So multiply 400 by 5 and then add 212


(400x5) + 212

The sum is about 2,212


**Compatible Numbers



28 x 9

Change one of the numbers to one you can easily work with


30x 9

The product is about 270