How do you solve $612-405$ ?

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Answer 1 · 2016-07-16T16:43:51

$207$

$612-405 = 207$

Use calculator or write out math

Answer 2 · 2016-07-17T08:59:18

207

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

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

How do you solve 612-405612-405?