Grandpa smiled and said:

"You know my cousin, lives in Florida, turned 85 yesterday. He told me that he walks thirty miles every day!"

"What? No way. That's more than 20 hours of walking!" I said

"True my son. But he is telling the truth. And no, he is not dreaming or that sort of thing" said Grandpa.

How can this be? How can a statement like that be true and false at the same time?


many of you might have read this as a joke somewhere. So did I. I just turned it into a humorous puzzle. Please let folks who have not seen this before solve it. Thanks

  • 1
    $\begingroup$ Right @Taco. Only the Humor tag. You will see why. $\endgroup$
    – DrD
    Aug 11, 2021 at 13:18
  • 2
    $\begingroup$ It strikes me that rot13(Guvegl Zvyrf vf n irel fgenatr anzr sbe n qbt...!) $\endgroup$
    – Stiv
    Aug 11, 2021 at 13:49
  • 2
    $\begingroup$ From the description of [humor]: "Please do not use this tag to post simple jokes which are not puzzles, and remember that questions should be uniquely answerable." - I don't know if this is applicable here, and I hope it isn't. Just noting. $\endgroup$
    – bobble
    Aug 11, 2021 at 14:29
  • 1
    $\begingroup$ Is he walking on the bus? $\endgroup$
    – Joshua
    Aug 12, 2021 at 3:05
  • 1
    $\begingroup$ Just noting... why is Grandpa replying to his grandchild as "True my son"? $\endgroup$
    – TRC
    Aug 12, 2021 at 16:12

7 Answers 7



his dog is named "thirty miles"? In which case I'm sure TM appreciates it

  • 2
    $\begingroup$ Doesn't fit with the reply "True". $\endgroup$
    – msh210
    Aug 11, 2021 at 15:14
  • $\begingroup$ Or, to vary it, perhaps he walks thirty dogs, all named Miles. $\endgroup$
    – Exal
    Aug 11, 2021 at 20:20
  • 5
    $\begingroup$ Maybe his other dog, "20 hours of walking", only gets walked every other day? $\endgroup$
    – Briguy37
    Aug 11, 2021 at 21:03
  • $\begingroup$ How does that make the statement be "true and false at the same time"? $\endgroup$
    – Wyck
    Aug 12, 2021 at 2:21
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    $\begingroup$ @msh210: It does fit, because grandpa is simply acknowledging that it would take over 20 hours to walk that far, but he is not saying that his cousin actually spends that amount of time walking. $\endgroup$
    – musefan
    Aug 12, 2021 at 9:36

- So he told you he once walked 30 miles?
- Yeah, and he told me that every day.

  • 6
    $\begingroup$ Doesn't really fit with the tenses used in the problem statement. $\endgroup$ Aug 12, 2021 at 0:44
  • $\begingroup$ This seems to be the best fit so far. $\endgroup$
    – justhalf
    Aug 12, 2021 at 6:02
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    $\begingroup$ Agree the question should be better worded, the tenses don't make much sense here. Every day, the 85-year-old cousin told Grandpa that he walks 30 miles. That's not true unless the cousin actually "walks 30 miles", and the tense here indicates that he does so in a repeated, ongoing sense. "I walk 30 miles" means that you have done it before, and intend to do it again. Similarly "I go to the gym on Thursdays" is false if you have no intention of going to the gym in the future, regardless of what you've done in the past. $\endgroup$ Aug 12, 2021 at 13:31
  • $\begingroup$ I agree, the tenses are a problem. But I like the answer anyway. $\endgroup$
    – Florian F
    Aug 13, 2021 at 11:43

Perhaps Grandpa is walking

thirty dogs named Miles simultaneously for about 40 minutes.

Doing the math, that would total about 20 hours of walking overall.

  • 2
    $\begingroup$ I'd argue the dogs must be named "Mile", or it would say he walked 30 Mileses. Clever answer! $\endgroup$ Aug 12, 2021 at 17:36

Clearly, he means that

He walked 30 miles every calendar day, over the course of his 85 years - so, 20 hours of walking in total on those 85 Jan. 1s, 85 Jan. 2s, etc.


It’s possible

they’re not talking about Earth days. 1 day on Mercury is about 58 Earth days and 1 day on Venus is 116 Earth days. Plenty of time to walk 30 miles. These guys might be astronomy buffs or something.


He does not walk 30 miles a day, obviously. However, the Earth rotates on its axis. So even though you are standing in the same place, you will still be moving through space.

That means, he walks slowly, the Earth moves. When he has moved 30 miles through space, he stops walking. So thats why the statement is true and false at the same time, because he did walk, moved a distance of 30 miles (through space), even though he did not walk that far ON EARTH.



He means the speed of the Earth. Earth rotates around its axis with the speed of 1,000 miles per hour, while moving around the Sun with the approximate speed of 67,000 miles per hour. Yes, he says that he walks only 30 miles, but probably he just acknowledges the achieving of his own goal of 30 miles every day.


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