Little Johnny failed his mathematics test completely.

His grade was so terrible that his teacher called home to speak with his father. When he got home that afternoon, his father stood crossly at the doorway. “Why did you fail your math test?” he inquired.

Little Johnny shrugged and replied: “My teacher isn’t very good.” Johnny’s father was astonished by his excuse and urged him to expand. “Well, on Monday, my teacher said 3+5 = 8.”

“So?” his father replied. “Then on Tuesday, she told us 4+4 = 8, and on Wednesday she said 6+2 = 8,” explained the child., “If she doesn’t know what equals eight, how am I supposed to know the right answer?”