1. Lesson #3
Estimation & Rounding

2. What is Rounding?
Estimation is used when we don’t know the exact value. It gives us a close, educated guess as to what the actual value is.
Example: Estimate how tall I am
Rounding is used to find an approximate value when we already know the exact amount
Example: Round my height to the nearest foot
You will always be asked to round a number to a certain place value
Numbers can be rounded up or rounded down

3. Rules for Rounding: ROUNDING DOWN:
4 or less: the number to the left remains the same – it is not ‘rounded up’ and the number you started with becomes a zero
Ex: ROUDNED TO THE NEAREST ONES/UNIT
= OR 591

4. Rules for Rounding: ROUNDING UP:
5 or more: the number to the left is ‘rounded up’ or increased by one and the number you started with becomes a zero
Ex: ROUDNED TO THE NEAREST ONES/UNIT
= OR 592

5. Just for fun: Rounding Rap 

6. Round to the nearest … ? Follow these steps for rounding numbers:
Find the number in the place value you are asked to round to (ones, tens, hundredths)
Look at the number in the place value to the right of it
If this number is 5 or more ___________
If this number is 4 or less ____________

7. Memorize : Place Value Chart

8. Examples: Use your place value chart to help you
Nearest tens
Nearest hundreds
Nearest thousandths
Nearest tenths
1270
450
10700
900
0.347
23.999
0.3
23.0

9. For your Notecard: ROUNDING
If the number you are rounding is followed by 5, 6, 7, 8, or 9, round the number up.
Example: 38 rounded to the nearest ten is 40
If the number you are rounding is followed by 0, 1, 2, 3, or 4, round the number down.
Example: 33 rounded to the nearest ten is 30
All the numbers to the right of the place you are rounding to become zeros.

10. Homework 
p. 9, #1 - 3
p. 10, #4-6
p. 11, #8 + 9
p. 12, #11 and #13