# Once youve decided where to round a number you need

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Once you’ve decided where to round a number, you need to look at thedigit immediately after where you want to round. You round up if thisdigit is 5 or more, and round down otherwise. When you round a number,you should state how it’s been rounded, in brackets after the roundednumber, as illustrated in the next example.Notice the ‘play button’ icon next to the following example. It indicatesthat the example has an associatedtutorial clip– a short video in which atutor works through the example and explains it. You can watch the clip,which is available on the module website, instead of reading through theworked example. Many other examples in the module have tutorial clips,indicated by the same icon.11
Unit 1AlgebraExample 2Rounding numbersRound the following numbers as indicated.(a) 0.0238 to three decimal places(b) 50 629 to three significant figures(c) 0.002 958 2 to two significant figuresSolution
Activity 2Rounding numbersRound the following numbers as indicated.(a) 41.394 to one decimal place(b) 22.325 to three significant figures(c) 80 014 to three significant figures(d) 0.056 97 to two significant figures(e) 0.006 996 to three significant figures(f)56 311 to the nearest hundred(g) 72 991 to the nearest hundred12
1NumbersThe use of the digit 0 to indicate an empty place in the representationA Babylonian clay tabletfrom around 1700 BCof a number seems essential nowadays. For example, the digit 0 in3802 distinguishes it from 382. However, many civilisations managedto use place-value representations of numbers for hundreds of yearswith no symbol for the digit zero. Instead, they distinguished numbersby their context. Evidence from surviving clay tablets shows that theBabylonians used place-value representations of numbers from at least2100 BC, and used a place-holder for zero from around 600 BC.When you need to round a negative number, you should round the partafter the minus sign in the same way that you would round a positivenumber. For example,0.25 =0.3 (to 1 d.p.).When you’re rounding an answer obtained from your calculator, it’s oftenuseful to write down a more precise version of the answer before you roundit. You can do this by using the ‘. . .’ symbol, like this:9.869 604 40. . .= 9.87 (to 2 d.p.).

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