What percent of 20 is 4?

20%
Very detailed answer. Shows 2 methods and also explains the difference between fraction and ratio
Using the shortcut method
If I were to be answering this for my self it would look like this
##4/20xx100=20%##
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Out of the 20 you have 4. So, as a fraction this is expressed as:
##” “4/20##
To change this to a percentage you multiply it by 100 giving
##” “4/20xx100##
which is the same as
##” “4xx100/20##
But ##100-:20 = 5## giving
##” “4xx5 = 20##
This needs to be expressed as a percentage so we write the 20 as:
##” 20 %”##
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##color(blue)(“A different approach”)##
##color(brown)(“% is a unit of measurement that is worth “1/100)##
The question means: 4 parts ##color(red)(ul(“in”))## every 20 parts.
##=>4/20=(“some value”)/100 = x/100##
##color(green)([ 4/20color(red)(xx1)] =x/100 )##
But ##5/5=1## giving:
##color(green)([ 4/20color(red)(xx5/5)] = [20/100]=x/100 )##
##20xx1/100″ ” =” ” x xx1/100##
But ##1/100## is the same as %
##20%” “=x%##
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##color(magenta)(“Very important note about difference between fraction and ratio”)##
Fraction:
##20/100 ->” “color(red)(ul(“within”))” the 100 you are looking at 20 parts”##
So the total count of parts is 100. Thus as a fraction of the whole you have ##20/100## as previously written.
In words this is: some count of parts ##ul(color(red)(“in”))## every 100 parts.
……………………………………………………………………………………………
Ratio in fractional format:
##20/100 ->” “color(red)(ul(“in addition”))## to 100 parts you are looking at the related ##” “##20 parts.
So the total count of parts is ##100+20 = 120##
In words this is: some count of parts ##color(red)(ul(“for”))## every 100 parts.
To change this to a fraction of the whole you would have: ## 20/120##