#### Georg Cantor was a mathematician who invented the branch of math known as set theory. He lived from 1845 to 1918.

Try this fun logic puzzle about time traveling to meet Cantor.

Professor Henderton from University College is obsessed with set theory and Georg Cantor. Ever since Henderton wrote his dissertation on Cantor’s theory of transfinite numbers, he has dreamed of meeting the brilliant mathematician.

Because Cantor died over 100 years ago, Professor Henderton is building a time machine to travel back to meet the brilliant mathematician. On campus, there is a lot of excitement about the time machine, and everyone is curious about which year Professor Henderton will visit on the maiden voyage.

Some people think that Professor Henderton will travel to a time long before Cantor was born to take credit (dishonestly) for inventing set theory. Other people think he will travel to when Cantor was alive to meet his hero. Still, others think he will travel to a year just after Cantor died to become the leader in the newly invented field.

An article in the school newspaper last week confirmed that the Professor would set a date for one of the following years:

- 1700
- 1750
- 1800
- 1850
- 1900
- 1950

Yesterday, a reporter for the school newspaper writing a follow-up article interviewed two of Professor Henderton’s assistants about the voyage date. Here is what each of them had to say:

Assistant #1 said, “The year is not 1750.”

Assistant #2 said, “The year is 1750, 1900, or 1950.”

Then, Assistant #1 said, “The year is not after 1869.”

Then Assistant #2 said, “The year is before 1812.”

Finally, Assistant #1 said, “The year is not 1800.”

The reporter accurately described his interview with the Professor’s two assistants. The assistants may be telling the truth or lying, but remember, an honest assistant is always honest, and an assistant who lies once will always lie.

Which year is Henderton going to visit on his inaugural trip?

## Try to solve it, then click to see the answer!

**The answer is 1850.**

Let’s suppose Assistant #1 is lying. If his first statement is false, then the year is 1750. However, if his last statement is false, the year is 1800. Since this is impossible, Assistant #1 must be telling the truth.

By Assistant #1’s first and last statements, we can eliminate both 1750 and 1800. His second statement tells us that the year is not after 1869, ruling out the years 1900 and 1950. This leaves 1700 and 1850 as the only possible years.

It’s now clear that Assistant #2 is lying. We know this because his first statement must be false since we know that the year is not 1750, 1900, or 1950. Since his second statement must also be false, the year is not before 1812. This eliminates 1700.

So, we can conclude that the time machine is set for 1850, just after Georg Cantor was born.