I and my friend are registering courses for the new semester. The math is on Tuesday 11.00-12.30. The physics is on Tuesday 9,40-12.30. I have registered the math. My friend asked if I want to register for physics. I said :"no." It is because math and physics are taught on the same day. When the physics class starts, the math class hasn't end. I couldn't quit the math class in the middle and go to the physics class. Could you teach me one way to explain? Thank you in advance.