Nasreddin once had an old boat, which he used to ferry people across the river. One day, he was taking a university professor to the other side.

• “What is the square root of 9?” asked the professor.
• “I don’t know,” answered Nasreddin.
• “How do you spell elephant?” asked the professor.
• “I have no idea,” replied Nasreddin.
• “Didn’t you study anything at school?” demanded the professor, surprised.
• “No,” said Nasreddin.
• “Then you wasted half your life,” said the professor.

Nasreddin was silent for a little while. Then he said:

• “Can you swim?”
• “No,” said the professor.

“Then you wasted ALL of your life,” said Nasreddin. “We are sinking.”