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=Estimating Sums and Differences (of decimals)=

Basically, estimating sums and differences with decimals is the same as doing it normally, but with another ones column. It has the same 4 and down and 5 and up rules, too. Front-end estimation with this is very different, and you may think it's easier. You just do the problem from the high columns to the low and not the decimals. Here are some good examples of front end estimation: 25.7 + 55.9= about 80, 90.5 + 12.3= about 102. Here are some examples of regular estimating with decimals ( to the nearest one): 15.7 + 72.3 First, the 15.7 gets rounded to a 16; then the 72.3 gets rounded back to a 72. The problem has now become 16+72=87. You could have rounded to tens afterward, too. Although, when you round to tens I'm pretty sure the decimals aren't really used. Rounding to the ones first will give you a more exact estimation, though.

Links http://www.mathleague.com/help/decwholeexp/decwholeexp.htm#estimating http://www.eduplace.com/math/hmm/practice/5/homework/11_4.pdf

Here's something that will help you with what place value is what: