Math Review of Estimating

Math Review of Estimating

Math Review of Estimating 150 150 Deborah

 

Overview:

Estimation is an important skill in mathematics, because sometimes an approximate figure is needed in everyday life.  Suppose a person is deciding if they have enough money to buy all the items on a shopping list or how many materials will be needed to finish a project.  Types of estimation include rounding up, rounding down, and rounding to the nearest.

Why Estimate?

Estimates are often used when an exact value is not available yet.  Suppose that a new road is being built.  Before companies can bid on the job, they will need to make an estimate of how much materials and labor will cost to build it.  Similarly, if people are going on a journey, they will need to estimate how much money they will need for the trip, as well as anything they might want to pack.  Also, sometimes estimates are easier to work with than exact figures.

What Is Rounding Up?

Many estimates involve “rounding up”.  Suppose the calculation for how many hours an individual works monthly shows that they will work 94.6 hours in the next month.  As this is only an estimate of how many hours they will work, it is usually rounded up to the next whole number.  They will work about 95 hours in the next month. Many small objects, such as pens, pencils, and paper clips are sold in boxes rather than individually.  If pens are sold is packages of 25, there will need to be at least 2 packages for a class of 42 students.

What Is Rounding Down?

Rounding down is a form of estimation where part of the amount is not taken into consideration.  For example, if the interest on a savings account is rounded down to the nearest cent, and the calculated interest is $15.242, only $15.24 would be paid out in interest.  Similarly, many calculators truncate any numbers past the 10th decimal place, so that a decimal such as .1236789452 would be read as .123678945. The directions that come with calculators tell how many places they will show.

What Is Rounding to the Nearest?

Usually when rounding numbers either up or down, more directions are given. The distance between the earth and the sun is 92,955, 807 miles. It is often rounded to the nearest million, or 93 million miles. Suppose the distance from the earth and the sun were given to the nearest 10 miles.  It would be rounded to 92,955, 810 miles.  Suppose it were given to the nearest 100 miles. Then the estimate would be 92, 955, 800 miles.

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