Mr. R.’s World of Math

Justin slowly woke-up from his snooze and complained, “I can’t believe I had to miss my football game for this! Now my team won’t go undefeated.”

     “Sure Justin, like just keep on bragging,” said Hannah, “I’m so sure your football team will do just fine without you. Probably even better!”
Mr. R. politely asked them to stop talking.
For the science lesson, Mr. R. was holding up two glass bottles that had chemicals in them. He said that if he mixed the two chemicals together they would probably react and vaporize the school.

(Well, maybe this isn’t what Mr. R looked like but….)

     David started shaking Greg to wake him up. “Hey Greg, wake up! Mr. R.’s gonna’ VAPORIZE the school. I think he’s gone mad!”
     “Whaaawhhhaaat, where am I?” asked Greg. It was now 1:28 and Greg had been sleeping since music class ended at 12:58.

How many minutes had Greg been asleep?