Fred has 15 cows
John has twice as many cows as Fred had
when Fred had as many cows as John has now
how many cows has John?
The logic is circular; thus, there is no answer. It is a literary version of an optical illusion such as the one where there is a set of descending stairs and the end of the stairs returns to the beginning.
Here is a slight rewording: Fred has as many cows as John has now, but john has twice as many cows. I first heard this riddle in a rerun of the 1957 TV show "The Rifleman", episode 17 (yesterday). The riddle is worse when all you can do is listen and not read it. So, I looked it up to ensure that I was understanding it correctly and here I am. 60 is NOT the answer. This is a dog chasing its own tail.
It takes about 15 seconds to realize there is no way to arrive at the answer. 15 cows, has nothing to do with the rest of the quest. Whoever wrote Mark McCain's text book should be fired ;).
60
John has no cows
A = cows Fred had before
B = cows Fred has now
J = cows John has now
B = 15
J = 2A
A = J
A = 2A --> A = 0
J = 2 * 0 = 0
60
Explain how you get 60. It seems to me as though there's insufficient information to solve this problem.
In order for John to have twice as many cows as Fred had when Fred had as many cows as John has now John has zero cows. Two times zero is zero.
I saw that “Rifleman” episode yesterday.
I agree that there is no conclusive answer.
Does anyone remember this riddle from that show:
“Where was the man when he jumped off the bridge”?
“In the air” - “no, that was after he jumped”.
“On the bridge” - no, that was before he jumped.
Ah, my wasted youth!
Moot
The logic is circular; thus, there is no answer. It is a literary version of an optical illusion such as the one where there is a set of descending stairs and the end of the stairs returns to the beginning.
Here is a slight rewording: Fred has as many cows as John has now, but john has twice as many cows. I first heard this riddle in a rerun of the 1957 TV show "The Rifleman", episode 17 (yesterday). The riddle is worse when all you can do is listen and not read it. So, I looked it up to ensure that I was understanding it correctly and here I am. 60 is NOT the answer. This is a dog chasing its own tail.
The 15 cows has nothing to do with the question. Therefore there is no figure involved with the question
It's like say I have cows you have twice as me
How many cowe do you have?
I agree with above, fire the text book writer, but what can you imagine being the rifleman and having to help Mark with his homework!?!?
I'm not sure zero is incorrect, since it works mathematically. Although it may just be a matter of semantics, this is an instance where equal and twice or even 100 times the number can all exit at the same time. Of course, one also could argue that there is no answer because the question poses a scenario in which Fred and John have cows. But zero means they don't have cows at all.
I just love this puzzle. It's actually fun getting people to think about it. I have a friend who has a doctorate in math and I posed it to him while he was driving. The flaws weren't apparent to him until he was able to ponder it later on, after he wrote it down. (I suggested that he offer this as an extra credit question when he gives a test for the college-level statistics course he teaches. I know this really isn't statistics. If fact, I think of it as a problem of logic instead of a math. But it's wonderful.)
But what also is really interesting is how it got into that Rifleman episode. Mark just reads it to Lucas, who kind of scratches his head. And that's it. They never go back to it or explain it or anything. It's sort a joke on the viewer who is left to try to figure it out. I consider this one of the gems of TV history. I would love to know how it got into the script and who came up with it, as well as the actors' reactions when they were filming it. They must have known about the flaws. I bet is was a laugh riot. I suppose someone could try reaching out to Johnny Crawford to see if he still remembers.
Incidentally, I rarely watched the Rifleman when I was young (though I asked my parents to get me a Rifleman rifle for Christmas). Now that I'm not my 60s, I've discovered what an amazing, well-intended show it was, not really about the violence at all, but basically morality plays that feel refreshing and hopeful in today's screwy world.
There is no answer, zero is incorrect also. Even though
2*0=0 it’s not twice as many, it’s the same amount. Therefore, the answer does not exist and now we know why Mark was having so much trouble with the question.