Editing Rounding (section)

==Types of rounding==
Typical rounding problems include:
{| class="wikitable" style="min-width: 40em"
|-
!Rounding problem
! style="width: 8.2em" |Example input
! style="width: 5em" |Result
!Rounding criterion
|-
|Approximating an irrational number by a fraction
| [[pi|{{pi}}]]
| 22/7
| style="white-space: nowrap;" |1-digit-denominator
|-
|Approximating a [[rational number]] by a fraction with smaller denominator
| 399 / 941
| 3 / 7
| 1-digit-denominator
|-
|Approximating a fraction by a fractional [[decimal number]]
|5 / 3
|{{math|1.6667}}
|4 [[significant figures|decimal places]]
|-
|Approximating a fractional [[decimal number]] by one with fewer digits
|{{math|2.1784}}
|2.18
|2 decimal places
|-
|Approximating a decimal [[integer]] by an integer with more trailing zeros
|{{math|23217}}
|{{math|23200}}
|3 significant figures
|-
|Approximating a large decimal [[integer]] using [[scientific notation]]
|{{math|300999999}}
|{{math|3.01 × 10{{sup|8}}}}
|3 significant figures
|-
|Approximating a value by a multiple of a specified amount
|48.2
|45
|Multiple of&nbsp;15
|-
|Approximating each of a finite set of real numbers by an integer so that the sum of the rounded numbers equals the rounded sum of the numbers<ref group="nb">This is needed e.g. [1] for the [[party-list proportional representation|apportionment of seats]], implemented e.g. by the [[largest remainder method]], see [[Mathematics of apportionment]], and [2] for distributing the total [[value-added tax|VAT]] of an invoice to its items)</ref>
| {{tmath|\bigl\{\tfrac3{12}, \tfrac4{12}, \tfrac5{12}\bigr\} }}
|{0, 0, 1}
|Sum of rounded elements equals rounded sum of elements
|}