"Logical and Math" joke

Two nuns, one known for her skill in math (M) and the other known for her skill in logic (L), were walking one dark night far from the convent when they noticed a man following them. M: Have you noticed that a man has been following us for the past thirty-eight and a half minutes? I wonder what he wants.
L: It`s logical. He wants to rape us.
M: Oh, no! At this rate he will reach us in 15 minutes at the most. What can we do?
L: The only logical thing to do of course is to walk faster.
M: It`s not working.
L: Of course it`s not working. The man did the only logical thing. He started to walk faster too.
M: So, what shall we do? At this rate he will reach us in one minute.
L: The only logical thing we can do is split. You go that way and I`ll go this way. He cannot follow us both.
So the man decided to follow the logical sister. The mathematical sister arrives at the convent and is worried about what has happened to her fellow nun. Then the logical sister arrives.
M: Sister Logical! Thank God you are here! Tell me what happened!
L: The only logical thing happened. The man couldn`t follow us both, so he followed me.
M: Yes, yes! But what happened then?
L: The only logical thing happened. I started to run as fast as I could and he started to run as fast as he could.
M: And?
L: The only logical thing happened. He reached me.
M: Oh, dear! What did you do?
L: The only logical thing to do. I lifted my dress up.
M: Oh, Sister! What did the man do?
L: The only logical thing to do. He pulled down his pants.
M: Oh, no! What happened then?
L: Isn`t it logical, Sister? A nun with her dress up can run faster than a man with his pants down.