Where does the heating process begin in a hot water heater system?

-- The pipes don't do any heating; they just carry stuff from one place to another.

-- The radiator's job is to LOSE heat ... it RADIATES heat from the hot fluid in the pipes out to the room that needs to be heated.

-- The BOILER is the place where you BOIL something, usually water, (using coal, oil, natural gas, radioactive Uranium, or electricity).  Then you push it THROUGH the pipes TO the radiator, where the heat it's carrying can shine out into the cold room and warm things up.  

the old price per ounce is c/4.

the new price per ounce is c/3.6.

the ratio of the old price to the new one is

(c/4)/(c/3.6) = (c/c)×(3.6/4) = 0.9 . . = 9/10 . . "nine tenths" in either form

answerscientific theory;