Estimation:
To replace all the digits of the number with zeros except for the largest place value digit>
Example:
325864 ==> 300000
12345789652 ==> 10000000000
Rounding:
To replace a number with a simpler close number
you can round up if the digit next door is 5 or more ,
and round down if the digit next door is 4 or less
Examples:
round the next number === > to the nearest
2315 to the nearest ten ==> 2320
51234 to the nearest hundred ==> 51200
