Write each statement as a proportion using colons. a. 4 is to 20 as 2 is to 10. b. 9 is to 27 as 2 is to 6.

Remark
You should always write proportions the way you normally do first. Most people write a proportion as
4/20 = 2 / 10  Using colons helps to make clear what is comparred all on one line.

4:20::2:10 

:: is the equal sign
/ is the division sign.
: (a single colon)  takes the place of /

9/27 = 2 / 6

Which can be 
9:27::2:6

Note
The colon method is not in current use as much as it was.

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He will need 2,898 pieces of paper