3A Mrs. Pagano

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Math Terminologies:

Period​: ​There are 2 periods: the ones and thousands.
Place- Where a digit is in each period.
Ex. 3,987 The 9 is in the hundreds place.

Place Value- The worth of a digit in its place.
Ex. 3987 The value of the 9 (in the hundreds place) is 900.

Ways We Write Digits:
S
tandard Form
- The way we write numbers everyday. 
Ex. 725
Expanded Form- This is the number written by first determining the place and then finding its value.
Ex. 700 + 20+  5
Written Form- This is the number written in words.
Ex. Seven hundred twenty five
ESTIMATION RULES:
1. Decide which 2 places the number is between.
Ex. 17 is between 10 and 20 
Ex. 168 is between 100 and 200
2. Look at the place value 
before the place you are rounding to. If that digit is 5 or higher round up. If it's 4 and lower round down.
Ex. If you're rounding to the 10's look at the 1's place. 17 would round to 20
Ex. If you're rounding to the 100's place look at the 10's place. 168 would round to 200
Ex, If you're rounding to the 1000's place look at the 100's place. 1,264 would round to 1,000
3. If you're rounding two different places always round both to the lowest place. This is used when we will be estimating sums. 
Ex. 34 + 489 would be 30 + 490 = 520 In this example both places would be rounded to the tens place.

ADDITION PROPERTIES:
Commutative Order Property- It doesn't make a difference which order 
the addends are in the sum is the same.
Ex. 4 + 5 =9 5+4 =9

Associative Order Property- It doesn't make a difference how you group the addends the sum is the same.
Ex. 3 + (2 +9)=14  or (3 + 2)+ 9=14
Identity Order Property- Any addend plus zero equals itself.
Ex. 6 + 0= 6