A. Rounding Up or Down
Rounding Up
Sometimes it makes sense to round a value up, regardless of what the digit is on the immediate right of the digit of interest.
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Example 2 |
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You need 13 m2 of wall paper. How many 4 m2 rolls should you buy? «math style=¨font-family:`Times New Roman`¨ xmlns=¨http://www.w3.org/1998/Math/MathML¨»«mfrac mathcolor=¨#B94A48¨»«mrow»«mn»13«/mn»«mspace width=¨0.33em¨/»«msup»«mi mathvariant=¨normal¨»m«/mi»«mn»2«/mn»«/msup»«/mrow»«mrow»«mn»4«/mn»«mspace width=¨0.33em¨/»«msup»«mi mathvariant=¨normal¨»m«/mi»«mn»2«/mn»«/msup»«/mrow»«/mfrac»«mo mathcolor=¨#B94A48¨»=«/mo»«mn mathcolor=¨#B94A48¨»3«/mn»«mi mathvariant=¨normal¨ mathcolor=¨#B94A48¨».«/mi»«mn mathcolor=¨#B94A48¨»25«/mn»«/math» Although the tenths digit is a 2, you cannot round this value down to 3 rolls because 3 rolls will not be enough to finish the project. You will need to buy 4 rolls of wallpaper. |
Rounding Down
Sometimes it makes sense to round a value down, regardless of what the digit is on the immediate right of the digit of interest.
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Example 3 |
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How many 15 cm strings can be cut from 100 cm? «math style=¨font-family:`Times New Roman`¨ xmlns=¨http://www.w3.org/1998/Math/MathML¨»«mfrac mathcolor=¨#B94A48¨»«mrow»«mn»100«/mn»«mspace width=¨0.33em¨/»«mi»cm«/mi»«/mrow»«mrow»«mn»15«/mn»«mspace width=¨0.33em¨/»«mi»cm«/mi»«/mrow»«/mfrac»«mo mathcolor=¨#B94A48¨»=«/mo»«mn mathcolor=¨#B94A48¨»6«/mn»«mi mathvariant=¨normal¨ mathcolor=¨#B94A48¨».«/mi»«mover mathcolor=¨#B94A48¨»«mn»6«/mn»«mo»§#9472;«/mo»«/mover»«/math» Although the tenths digit is a 6, you cannot round this value up to 7 because you are looking for the number of 15 cm strings. You can only cut 6 strings of full length. |
Often when a value is rounded, the equality sign is replaced by an approximately equal to symbol, such as «math xmlns=¨http://www.w3.org/1998/Math/MathML¨» «semantics» «mstyle mathcolor=¨#000000¨ mathsize=¨12.0pt¨ mathvariant=¨normal¨» «mo» §#8784; «/mo»
«/mstyle» «/semantics» «/math» or «math xmlns=¨http://www.w3.org/1998/Math/MathML¨» «semantics» «mstyle mathcolor=¨#000000¨ mathsize=¨12.0pt¨ mathvariant=¨normal¨» «mo» §#8776; «/mo» «/mstyle» «/semantics» «/math» to show that the two sides of the
equation are not exactly equal and that rounding of some kind has occurred.
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Example 4 |
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«math style=¨font-family:`Times New Roman`¨ xmlns=¨http://www.w3.org/1998/Math/MathML¨»«mfrac»«mn»10«/mn»«mn»3«/mn»«/mfrac»«mo»=«/mo»«mn»3«/mn»«mi mathvariant=¨normal¨».«/mi»«mn»3333«/mn»«mi»...«/mi»«/math» «math style=¨font-family:`Times New Roman`¨ xmlns=¨http://www.w3.org/1998/Math/MathML¨»«mfrac mathcolor=¨#B94A48¨»«mn»10«/mn»«mn»3«/mn»«/mfrac»«mo mathcolor=¨#B94A48¨»§#8784;«/mo»«mn mathcolor=¨#B94A48¨»3«/mn»«mi mathvariant=¨normal¨ mathcolor=¨#B94A48¨».«/mi»«mn mathcolor=¨#B94A48¨»3«/mn»«/math» |