Simplify the following text for a Grade 10 native English-speaking person.
Original: The colon is also used in mathematics , cartography , model building and other fields to denote a ratio or a scale , as in 3:1 ( pronounced `` three to one '' ) .
Simplified: The colon is used in mathematics , cartography , model building and other fields to denote a ratio or a scale , as in 3:1 ( pronounced â three to oneâ ) .