Rounding Decimals: Helping Your Elementary Students Learn Estimation of Decimals

rounding decimalsIf you teach fifth grade, you might be looking for some resources on teaching your students how to round decimals. Rounding decimals is a particular skill students need to help them with complex estimation problems. Use the tips and resources below to help you better reach your students and teach them rounding decimals. Learn beginning algebra with an online class.

Rules for Rounding

As with most mathematical theories, there are particular rules involved when it comes to rounding decimals. The first is to keep the proper number of decimal places. If you’re rounding to the hundredths place, you don’t omit the tenths place. The second rule is to remember the rounding rules for whole numbers – use the number to the right of the place value you’re rounding to find out how you’re going to round. Study Algebra I with an online course.

Methods for Rounding

There are several different methods that can be used for rounding beyond the common method. Each method is detailed below. You can also check out Math is Fun’s page on rounding methods for number line graphics and more. Learn the fundamentals of math with an online class.

Half Round Up

Considered the common method of rounding, this is the method you would recognize from school. It involves taking a number like 7.647 and rounding up. If you were rounding 7.647 to the nearest hundredths, you would use the 7 on the right of the 4 to decide what to do about the 4. Because the 7 is higher than 5, you’re going to change the 4 to a 5. 7.647 rounded to the nearest hundredths is 7.65.

Half Round Down

This particular rounding method is rarely used in schools as it involves ignoring the common rules for rounding numbers. Consider the number 8.45 and round it to the nearest tenths place. Using the half round up, you would look at the number to the right of the 4, find that it’s a 5 and come up with 8.5, but the half round down answer is different. Using this particular rounding method, a 5 would actually round down just like any number 0-4 would. So, the answer for 8.45 when rounded to the nearest tenths would be 8.4 instead.

Symmetric Rounding

When dealing with negative numbers, your answers can often be the opposite of what they would be for their positive counterparts. For example, -7.647 rounded up to the nearest hundredths would actually be -7.64 because that is the higher number, as opposed to -7.65, which would be going down. Instead of doing that, however, you could teach the method of symmetric rounding in which the positive and negative answers would be the same because you would be rounding toward or away from zero.

Round to Even

To avoid a bias and have a more accurate estimated answer when rounding, you should consider the method of rounding to even. This method is useful only for numbers ending in 0.5 as the 5 is what decides what even number the number will be rounded to. As an example, 8.5 rounds down to 8 because eight is an even number, but 9.5 would round up to ten because ten is the closest even number. Numbers that don’t end in 0.5 would round as usual – 8.4 and lower would round to 8, and 8.6 and higher would round to 9. This is a great method for turning decimals into whole numbers.

Round to Odd

Like the round to even method, this method is useful for rounding decimal numbers to whole numbers. Also like the round to even method, this method is useful only for numbers ending in 0.5, but instead of heading for the closest even number you’re heading for the closest odd number. For example, 8.5 would no longer round down to 8, but it would round up to 9 because that is the closest odd number. The same could be said for 9.5, which would no longer round up to ten but round down to 9 because 9 is the closest odd number. Again, numbers that don’t end in 0.5 would round as usual.

Floor and Ceiling Rounding

Like rounding to even and rounding to odd, this particular method of rounding would round decimal numbers to whole numbers. Using the floor rounding method, any decimal would round to the whole number within the decimal. For example, 6.547 would round to 6. 6.795 would also round to 6. Any number from 6 to 6.99999999 (and so on) would round to 6 with the floor method.

The ceiling method rounds in the opposite direction of the floor method. Anything from 6.00000001 (and so on) to 6.99999 (and so on) would round up to 7, but 6 would stay 6. Using these two methods together will give you the nearest integers going up or down on a number line. Learn mental math with an online course.

Resources for Rounding Help

If you’re a teacher, there is nothing that says you have to come up with completely original stuff to teach your students. Even before the creation of the internet, teachers would share information with other teachers. There are entire books published with helpful lesson plans on any subject. So, when it comes to teaching your students how to round decimals, don’t think you have to do it on your own. Try using some of these resources below. Read an article on the importance of school to remind yourself why you became a teacher.

Worksheets

Though not a great teaching tool, worksheets can be a great practice tool for students when doing independent study. Common Core Sheets offers some great worksheets for rounding both whole numbers and decimals. You can also get your students started on some estimation problems if they’ve gotten the hang of rounding.

Another great site for rounding worksheets is Math-Aids, which offers worksheets on rounding whole numbers, decimals, and even money. There are also charts you can print out as a guide for your students that need just that little bit of extra help with rounding.

Tools

Math is Fun has a great rounding tool that allows students to instantly see how each of the rounding methods above work. There is also a rounding calculator available through Calculator Soup. Along with the calculator, Calculator Soup lists the basic rules of rounding.

One last thing…

As stated before, you should never be afraid to use your resources as a teacher. If you have a coworker who has been teaching at the school for many more years than you, consider asking him or her how they might teach rounding decimals. Don’t forget that students have different learning styles, so try to teach using various approaches. Offer a variety of tools that your students can use to help them. The most important thing is to teach them how to round without your help.