Decimals – Help With Rounding Decimals

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     When we ‘round’ decimals, we make an approximation. 

     For example, the decimal number 0.023 could be rounded to 0.02.  We can forget about the digit in the thousandths column (i.e. the 3).  Since ‘3’ is less than 5, we don’t touch the number in the hundredths column (i.e. the 2).

      If we had the decimal number 0.025, we would round it to 0.03 because we round up when the number to the right is 5 or greater.

     When we round a number we are making them ‘shorter’ according to their decimal places.  The rules for rounding are simple:

     When rounding a number, if the digit to the right of the digit we are rounding is greater or equal to 5, we eliminate it and make the digit to the left 1 greater.

     Examples: 

0.075 rounded to the nearest hundredth becomes 0.08

0.249 rounded to the nearest hundredth becomes 0.25

0.46 rounded to the nearest tenth becomes 0.5

     The next part of the rules states that if the digit to the right of the digit we are rounding is less than 5, we eliminate out the numbers to the right and leave the number to the left as it is.

     Examples:

0.074 rounded to the nearest hundredth becomes 0.07

0.243 rounded to the nearest hundredth becomes 0.24

0.41 rounded to the nearest tenth becomes 0.4

     Make sure your child is aware of the fact that sometimes he or she may be asked to look at the digit in the thousandths place and round the number to the nearest tenth.

     For example, assume you were asked to round the number 46.317 to the nearest tenth.  Okay.  Don’t bother looking at the number in the thousandths place (i.e. the 7).  Since you are being asked to round to the nearest tenth, you have to look at the number in the hundredths place.  In this case, the number is 1, so we leave the 3 and the answer is 46.3.

     Having a good understanding of decimal place value will help your child effectively round decimal numbers.

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 Learn'Em Good - Fractions and Decimals - by Stuart Ackerman MSc.Ed.,B.A.

Easy to Use Lessons and Worksheets to Help Improve Your Grade 1-8 Child's Fraction and Decimal Skills