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Dŵr y Felin Comprehensive School Rounding Methodology Booklet Rounding To whole numbers Examples 1. Round 1.4 to the nearest whole number 1 1.5 2 1.4 is clearly closer to 1 than 2, so it rounds to 1 2 Technically 1.5 is in the middle, but we always round up 0.5 to the next whole number in this case 2 1.4 2. Round 1.5 to the nearest whole number 1 1.5 Summary To round to the place value required look to the number to the right: 4 or less - the number stays the same (round down) 5 or more - the number increases by 1 (round up) More examples Round 65293.4 to the nearest:Whole number (integer) 6 5 2 9 3 . 4 = 65293 Look to the figure to the right. It is 4 or less so round down 6 5 2 9 3 . 4 = 65290 Look to the figure to the right. It is 4 or less so round down Hundred 6 5 2 9 3 . 4 = 65300 Look to the figure to the right. It is 5 or more so round up Thousand 6 5 2 9 3 . 4 = 65000 Look to the figure to the right. It is 4 or less so round down Ten Rounding To Decimal Places Round 6.99 to 1 decimal place (1dp) It is easier to see this on a number line. 6.99 6.8 6.9 7.0 7.1 6.99 is now clearly closer to 7.0 than 6.9 so we have to round up to 7.0 Examples Round 9.86287 to:1 decimal place 9.86287 Look to the figure to the right. It is 5 or more so round up. 2 decimal places 9.86287 Look to the figure to the right. It is 4 or less so round down. 3 decimal places 9.86287 Look to the figure to the right. It is 5 or more so round up. Rounding Significant Figures Significant Figures and Whole Numbers Remember that significant figures are always counted from the first non-zero digit. Example For the number 284.36 284.36 Significant figure - 1st 2nd 3rd 4th 5th the 2 is the first significant figure the 8 is the second significant figure the 4 is the third significant figure etc. It is important to remember that rounding a number gives an approximate value for that number. It is used when the exact value is not needed. For example, on one day of the London Olympics there were 892,654 spectators at the events. Most people would not need to know this exact figure and would be happy with approximate values of about 890,000 or nearly 900,000. Notice that the approximate values have been “filled-in” with zeroes to keep the same order of size. Examples Round 76452 to:1 significant figure 7 6 4 5 2 = 80,000 Look to the figure to the right. It is 5 or more so round up. 2 significant figures 7 6 4 5 2 = 76,000 Look to the figure to the right. It is 4 or less so round down. 3 significant figures 7 6 4 5 2 = 76,500 Look to the figure to the right. It is 5 or more so round up. Rounding Significant Figures and Decimals Remember that significant figures are always counted from the first non-zero digit. Example For the number 0.04637 0.04 6 3 7 Significant figure - 1st 2nd 3rd 4th the 4 is the first significant figure the 6 is the second significant figure the 3 is the third significant figure etc. It is important to keep the same number of zeros between the decimal point and the first significant figure but there is no need to put zeros after the “rounded” digit. Examples Round 0.002736 to:1 significant figure 0.002 736 = 0.003 Look to the figure to the right. It is 5 or more so round up. 2 significant figures 0.0027 36 = 0.0027 Look to the figure to the right. It is 4 or less so round down. 3 significant figures 0.00273 6 = 0.00274 Look to the figure to the right. It is 5 or more so round up.