Editing Multiplication algorithm (section)

===Grid method===
{{main|Grid method multiplication}}
The [[grid method multiplication|grid method]] (or box method) is an introductory method for multiple-digit multiplication that is often taught to pupils at [[primary school]] or [[elementary school]].  It has been a standard part of the national primary school mathematics curriculum in England and Wales since the late 1990s.<ref>{{cite news |first=Gary |last=Eason |url=http://news.bbc.co.uk/1/hi/education/639937.stm |title=Back to school for parents |publisher=[[BBC News]] |date=13 February 2000}}<br>{{cite news |first=Rob |last=Eastaway |author-link=Rob Eastaway |url=https://www.bbc.co.uk/news/magazine-11258175 |title=Why parents can't do maths today |publisher=BBC News |date=10 September 2010}}</ref>

Both factors are broken up ("partitioned") into their hundreds, tens and units parts, and the products of the parts are then calculated explicitly in a relatively simple multiplication-only stage, before these contributions are then totalled to give the final answer in a separate addition stage.

The calculation 34 × 13, for example, could be computed using the grid:
<div style="float:right">
<pre>  300
   40
   90
 + 12
 ————
  442</pre></div>
{| class="wikitable" style="text-align: center;"
! width="40" scope="col" | ×
! width="40" scope="col" | 30
! width="40" scope="col" | 4
|-
! scope="row" | 10
|300
|40
|-
! scope="row" | 3
|90
|12
|}

followed by addition to obtain 442, either in a single sum (see right), or through forming the row-by-row totals 
: (300 + 40) + (90 + 12) = 340 + 102 = 442.

This calculation approach (though not necessarily with the explicit grid arrangement) is also known as the [[partial products algorithm]].  Its essence is the calculation of the simple multiplications separately, with all addition being left to the final gathering-up stage.

The grid method can in principle be applied to factors of any size, although the number of sub-products becomes cumbersome as the number of digits increases. Nevertheless, it is seen as a usefully explicit method to introduce the idea of multiple-digit multiplications; and, in an age when most multiplication calculations are done using a calculator or a spreadsheet, it may in practice be the only multiplication algorithm that some students will ever need.