How do you convert 1/5 into a percent and decimal?

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Answer 1 · 2016-05-17T11:58:01

$1/5->0.2$

$1/5->20/100->20%$

$color(blue)("Convert "1/5" into decimal")$

$color(brown)("Shortcut method"$

divide 5 into 1

But 1 is less than 5

Known: multiply anything by 1 and you do not change its value.

Suppose we had $1/5 xx 1$ but wrote it as $1/5xx10/10$

This is the same as $(1xx10)/5xx1/10" " ->" " 10/5xx1/10$

Which is the same as $2xx1/10" " ->" " 2/10 =0.2$

'........................................

$color(brown)("Another approach")$

As the first decimal place is measuring/counting in tenths and you recognise that $2xx5=10$ then do this:

Multiply by 1 but in the form of $1=2/2$ giving

$1/5xx2/2" "=" "(1xx2)/(5xx2)" "=" "2/10 ->color(magenta)( 0.2)$
'~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
$color(blue)("Convert "1/5" into percent")$

$color(brown)("Shortcut method")$

$1-:5 xx 100" " =" "color(magenta)( 0.2)xx100" " =" " 20%$

This is the same as $20/100$