Question

How do you solve `612-405`?

Answer 1

`207`

Explanation:

`612-405 = 207`

Use calculator or write out math

Answer 2

207

Explanation:

There are several ways this type of question can be approached. I am going to show you two methods.

`color(blue)("Method 1 - Splitting the numbers (partitioning)")`
Write `612" as "600+12`
Write `405" as "400+5`

Now write them as:

`" "600+12`
`" "ul(400+5)larr" Subtract"`
`" "200+7`

Answer `207`
'~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
`color(blue)("Method 2 - This is the more traditional way")`

`color(brown)("It is the same thing as method 1 but in disguise")`

Write as:

`" "61color(magenta)(2)`
`" "ul(40color(magenta)(5))`

`color(magenta)("Consider the right hand column (units)")`

The 2 is less than 5 so move one of the tens to the units. Then the 1 in 12 becomes 0 and the 2 in 12 becomes `10+2=12` giving

`" "6cancel(1)^0 cancel(2)^(12)`
`" "ul(4color(white)(.)0color(white)(.)5) larr" Subtract"`
`" "2color(white)(.)0color(white)(.)7`