Rounding up and down

One of the most important tasks you have to be able to perform competently, on a daily basis, is estimation of an answer. One of the skills which enables us to do the estimation with relative speed and accuracy is "rounding up and rounding down".
The same rule applies to each place value column in a numeral regardless of whether you are changing to the nearest ten, hundred, thousand etc.
Look at the digit to the right hand side of the place value you're rounding to; if it's 5 or greater add one to the"rounded to" column; if it's less than 5 leave the "rounded to" column as is. eg 45 x 54 becomes 50 x 50.
Multiply the digits ignoring the zeros, then add the total number of zeros in both the factors to the right hand end of your answer. eg 45 x 54 becomes 50 x 50 = 5x5 = 25 now add the zeros and the estimation is 2500.