Simplify the following text for a Grade 6 native English-speaking person.
Original: Last , the host lets the player choose whether to keep what is behind the first door or to change choices to the third door ( the one the host did not open ) .
Simplified: If the car is actually behind Door 1 ( the door chosen by the contestant ) , the chance the host will open Door 3 is 0.5 ( both doors are equally likely to be opened when the host has a choice ) .