Rounding In Context.

 

By the time students arrive in high school, they have been exposed to the normal rules associated with rounding.  You know the one where they look at one place past the one they want to round and use that to determine if they round up or down.  That works well in a theoretical situation but it doesn't always work in real life.  Not everything that is rounded follow the rules of if it is five or more, round up and four and lower round down.

Bankers have their own way of rounding that doesn't follow these rules for taxes.  If the calculated value ends in five, and the value in the cents place is even, it is rounded down. For instance if you have a 8.5 percent tax rate then you would have $1.085 after adding in the tax. So it ends in 5 but there is an 8 in the cents place but the rule says if the number in the cents place is even, it rounds down so it will show as $1.08.  How ever if you spent $15.00 with a tax rate of 8.5 percent, you end up with a tax of $1.275.  This ends in 5 but there is an odd number in the cents place so this is rounded up to the next digit so tax is $1.28 for a total of $16.28.  Now if you have a weird rate like 6.8% and the tax ends in any other number but 5, the normal rules of rounding apply.  So you spend $15.28 and tax is $1.039. Since 9 is not a 5, this means the regular rules of rounding are applied and this rounds to $1.04 for a total of $16.32. This type of rounding also applies to transaction fees and other such items.

On the other hand, paint is something you do not want to round down on since you want to have enough paint to finish the project.  It has been suggested by Bob Villa that you round up to the closest quart so you buy just a bit extra but not too much.  If you calculate all the area you want to paint in a room and come up with 4.3 gallons of paint, the normal rules say you round down to 4 gallons but 4 gallons may not be enough since .3 is a third of a gallon.  Instead, you might round it up to 4.5 so you have enough paint but not too much.  If how ever you end up needing 4.03 gallons, you might round it up to 4 gallons and 1 quart.  When dealing with items such as paint, primer, water seal, etc that are expressed as one gallon covering so much area, you might think in gallons with quarts at .25, .5, and .75.

Another area for rounding is when you are buy carpeting. The easiest way to figure out the amount of carpeting needed for a room.  If you want to measure it yourself, it is recommended that all measurements be rounded up to the next half or whole foot.  So if one dimension is 4 feet 3 inches, round it from 4.25 to 4.5 and if the other dimension is 8 feet 7 inches, round it up to 9 feet.  This way people make sure they have enough carpeting for the job.  This is a always round up situation.  It is also suggested that one add in five percent to cover seams.  The total number of square feet are divided by 9 because there are 9 square feet in one square year.  The answer is then rounded up to a whole or half a yard.

These are examples where the standard rules of rounding do not apply since in many situations one has to round up so there is enough material to finish a project.  These are just three situations but there are more where one rounds up.  Let me know what you think, I'd love to hear.  Have a great day.