Question 1039386
losing one key is the same as randomly drawing one key out of the 6.


there are 2 keys in the set of 6 that you need to open the door.
there are 4 keys in the set of 6 that you don't need to open the door.


the probability that the key that you draw will not be one of the 2 keys that you need is therefore 4/6 = 2/3.


the probability that you can still get in your house is therefore 2/3 because that's the probability that the key that is lost is not one of the 2 keys that you need.