Editing Elementary arithmetic (section)

=== Example of multiplication for multiple-digit factors ===
Multiplying 789 and 345, starting with the ones column, the product of 789 and 5 is 3945.
{|style="border-collapse: collapse; border-spacing: 2px; text-align:center"
| ||7 ||8 ||9
|-
|style="border-bottom: 1px solid black;"|× ||style="border-bottom: 1px solid black;"|3 ||style="border-bottom: 1px solid black;"|4 ||style="border-bottom: 1px solid black;"|5
|-
|3 ||9 ||4 ||5
|}

4 is in the tens digit. The multiplier is 40, not 4. The product of 789 and 40 is 31560.
{|style="border-collapse: collapse; border-spacing: 2px; text-align:center"
|-
|
| ||7 ||8 ||9
|-
|
| style="border-bottom: 1px solid black;" |× || style="border-bottom: 1px solid black;" |3 || style="border-bottom: 1px solid black;" |4 || style="border-bottom: 1px solid black;" |5
|-
|
|3 ||9 ||4 ||5
|-
|3
|1 ||5 ||6 ||0 
|}

3 is in the hundreds digits. The multiplier is 300. The product of 789 and 300 is 236700.
{| style="border-collapse: collapse; border-spacing: 2px; text-align:center"
|
|
| ||7 ||8 ||9
|-
|
|
|style="border-bottom: 1px solid black;"|× ||style="border-bottom: 1px solid black;"|3 ||style="border-bottom: 1px solid black;"|4 ||style="border-bottom: 1px solid black;"|5
|-
|
|
|3 ||9 ||4 ||5
|-
|
|3
|1 ||5 ||6 ||0 
|-
|2
|3
|6 ||7 ||0 ||0 
|}

Adding all the products,
{|style="border-collapse: collapse; border-spacing: 2px; text-align:center"
| || || || ||7 ||8 ||9
|-
|style="border-bottom: 1px solid black;"|× ||style="border-bottom: 1px solid black;"| ||style="border-bottom: 1px solid black;"| ||style="border-bottom: 1px solid black;"| ||style="border-bottom: 1px solid black;"|3 ||style="border-bottom: 1px solid black;"|4 ||style="border-bottom: 1px solid black;"|5
|-
| || || ||3 ||9 ||4 ||5
|-
| || ||3 ||1 ||5 ||6 ||0
|-
|style="border-bottom: 1px solid black;"|+ ||style="border-bottom: 1px solid black;"|2 ||style="border-bottom: 1px solid black;"|3 ||style="border-bottom: 1px solid black;"|6 ||style="border-bottom: 1px solid black;"|7 ||style="border-bottom: 1px solid black;"|0 ||style="border-bottom: 1px solid black;"|0
|-
| ||2 ||7 ||2 ||2 ||0 ||5
|}

The result:

:<math>789 \times 345 = 272205</math>