Question: There are 5 people in a room. I came & killed 4. How many remain?
Answer: In the room, there are already 5 peoples. so, the number of persons in the room is 5.
You enter into the room later. Now, the number of persons will be
= 5 + 1 = 6
You killed 4, so the number of persons alive are 2 in the room.
But the question is asked to find out the number of persons both alive and dead. Hence, the answer will be 6 persons remain inside the room.