In a physics course, which involved light, electricity and magnetism, the students were required to read the week's experiment before coming to class. At one lab session the student assistant wanted to see how many of his pupils had actually done so.
"What are the two types of light?" he asked.
The lab fell quiet until one wise guy raised his hand and said, "Uhhh, Actually there are three: Bud, Coors and Miller!"
The master, to impress on his pupils the need of thinking before speaking, told them to count to fifty before saying anything important, and one hundred if it was very important.
Next day he was speaking, standing with his back to the fire, when he noticed several lips moving rapidly.
Suddenly the whole class shouted: "Ninety eight, ninety-nine, one hundred... Your coat's on fire, sir!"