Easy one

Milos · 2005-05-12 11:36:42

In the first 12 hours snail climbs 3m, and in next 12 hours it slides down 2. If a column is 20m high, when will snail reach the top of it?(e.g. on the 5th day)

Zach · 2005-05-12 20:39:01

Each day, apparently, it moves up 1m. Thus, it, logically, should take, taking into account the theory that a day is 24 hours in length instead of 23 hours and 57 minutes, should be on the 20th day the snail reachs the top, if still alive.

In truth, a French man has arrived and eaten Mr. Snail.

Milos · 2005-05-12 22:38:45

No Zach, that is not correct. I will leave it unsolved, because I want others to try.
There is not a French man who eats it, and all parameters needed for solving puzzle are given.

Zach · 2005-05-13 04:35:35

How is it incorrect. If the snail makes it up 1m of the wall per day, then in all logical circumstances he will make it up the whole wall in 20 days. 3 - 2 ( per 24 hours) = 1.

Zach · 2005-05-13 04:40:36

Each day it moves up 3m in the first half...
20 x 3 = 60 metres.
Then, every day it falls down 2m.
20 x 2 = 40 metres.
----------------------
Subtracting the lower from the higher = 20 days.

Milos · 2005-05-13 05:39:32

OK. For one day it climbs 1m(I agree with that ; 3-2=1), but when it comes to 17m(17th day) , it has 3m to reach the top. As it climbs 3m for 12h, he will reach the top on 18th day.

MathsIsFun · 2005-05-13 10:01:06

Darn, he's RIGHT!

OK, try this:

In the library there is an "encyclopedia of worms". It is three volumes long, each volume has exactly 1000 pages and they are placed neatly on the shelf side-by-side. It takes the worm one hour to chew through 100 pages and it takes half an hour to chew through a cover.

If the worm starts at Page One of the First Volume and chews through to Page 1000 of the Last Volume, how long does it take?

Warning: I don't know the answer, but I know that there are possible wrong assumptions.

stewie · 2005-05-13 10:04:57

32 hours?

MathsIsFun · 2005-05-13 10:07:20

Hmmm, I don't know the answer, but that looks too high.

Zach · 2005-05-13 10:43:41

Milos wrote:

OK. For one day it climbs 1m(I agree with that ; 3-2=1), but when it comes to 17m(17th day) , it has 3m to reach the top. As it climbs 3m for 12h, he will reach the top on 18th day.

Incorrect, though I see your logic.

The answer is the 17th day with this new answer. On the 18th day, he'd be at 18m.

Zach · 2005-05-13 10:47:01

MathsIsFun wrote:

Darn, he's RIGHT!
OK, try this:
In the library there is an "encyclopedia of worms". It is three volumes long, each volume has exactly 1000 pages and they are placed neatly on the shelf side-by-side. It takes the worm one hour to chew through 100 pages and it takes half an hour to chew through a cover.
If the worm starts at Page One of the First Volume and chews through to Page 1000 of the Last Volume, how long does it take?
Warning: I don't know the answer, but I know that there are possible wrong assumptions.

IF he starts at page one, the worm'll take; 3( 1000/100 )+5(Covers), which'll equal: 10 hours per book + 5 Covers. Which'll equal Thirty Two Hours and Thirty Minutes.

MathsIsFun · 2005-05-13 10:50:40

Good maths, but look at the books on a shelf.

Zach · 2005-05-13 10:52:37

The Shelf breaks under all the pressure of the giant books and the poor worm is crushed.

Milos · 2005-05-13 13:30:05

Zach wrote:

Milos wrote:
OK. For one day it climbs 1m(I agree with that ; 3-2=1), but when it comes to 17m(17th day) , it has 3m to reach the top. As it climbs 3m for 12h, he will reach the top on 18th day.
Incorrect, though I see your logic.
The answer is the 17th day with this new answer. On the 18th day, he'd be at 18m.

after 1st day-1m
after 2nd day-2m
after 3rd day-3m
after 17th day-17m
day-24h
now, as there are 3m left, in the first part of 18th day (first 12h) it will reach the top. So it is 18th day, not 17th. It doesn't need to go back when it has reached the top -or if it does, that does not interest us. Question was:' When will it reach the top', so if it wants to jump after reaching the top that is its problem, not ours.
I hope you understand it know. My answer is correct, I assure you.

Milos · 2005-05-13 13:37:55

I would like you to try "What should be the question" puzzle - that one is much more difficult, and more interesting. - some members have mentioned that you can solve it. Can you?

Zach · 2005-05-13 20:35:23

Milos wrote:

Zach wrote:
Milos wrote:
OK. For one day it climbs 1m(I agree with that ; 3-2=1), but when it comes to 17m(17th day) , it has 3m to reach the top. As it climbs 3m for 12h, he will reach the top on 18th day.
Incorrect, though I see your logic.
The answer is the 17th day with this new answer. On the 18th day, he'd be at 18m.
after 1st day-1m
after 2nd day-2m
after 3rd day-3m
after 17th day-17m
day-24h
now, as there are 3m left, in the first part of 18th day (first 12h) it will reach the top. So it is 18th day, not 17th. It doesn't need to go back when it has reached the top -or if it does, that does not interest us. Question was:' When will it reach the top', so if it wants to jump after reaching the top that is its problem, not ours.
I hope you understand it know. My answer is correct, I assure you.

I don't think we're talking about the squirrel anymore!

But, anyway, I understand your logic. Yes.

jam-pot · 2005-05-15 22:53:18

erm yeah i agree it takes 18 days on account of it cannot slide down before it goes up so the last 3 m must be reached before it can fall down so it does reach the peak of 20m in 18 days

MathsIsFun · 2005-05-15 23:00:21

OK, now, back to my encyclopedia of worms puzzle ... Not Solved Yet!

stewie · 2005-05-16 03:10:24

i told already told u - 32 hours

Zach · 2005-05-16 05:15:50

You don't even know the answer! Which is blatently 32 Hours and 30 minutes.

Milos · 2005-05-16 06:38:24

OK, I thought of something else. If books are placed very neatly on shelf side-by-side than this could be correct. Take three books and organize them as they do it in libraries(so we could read the title of a book)- vertically. Start counting from left to right(as we usually do). You will see that your first page is 1000th. That would mean that in 12 hours worm will chew from 1st page of the first book to 1000th page of the last. 4 covers + 1000 pages of the book in the middle.

Last edited by Milos (2005-05-16 06:50:57)

Roraborealis · 2005-05-16 08:23:34

10 hours for normal pages in a volume. Three of these, so 30 hours.
If the worm starts at page one, then it doesn't chew the first cover, OR the last since it finishes at page 1000 of the last volume, it chews 4 covers. This totals 2 hours, so just 32 hours (one and a half days).

Milos · 2005-05-16 08:42:29

Yes, that is obvious, so than it wouldn't be a puzzle- or at least not a good one. I remember that I have been working on similar or maybe the same puzzle before so that's why I suggested this solution. I would like administrator's comment on this, if possible.

MathsIsFun · 2005-05-16 10:34:02

Indeed!

When books are placed on a shelf, the pages are like:

[ Volume 1 ][ Volume 2 ][ Volume 3 ]
[Page 1000 ... Page 1][Page 1000 ... Page 1][Page 1000 ... Page 1]

So, it is a tricky puzzle. I could have made it harder by saying the worm chews 100 SHEETS in an hour and you may have fallen into the trap of sheets vs pages, but I didn't (because I am nice )

Roraborealis · 2005-05-16 19:02:25

Oh, so it's not logic? Just maths?

Math Is Fun Forum

#1 2005-05-12 11:36:42

Easy one

#2 2005-05-12 20:39:01

Re: Easy one

#3 2005-05-12 22:38:45

Re: Easy one

#4 2005-05-13 04:35:35

Re: Easy one

#5 2005-05-13 04:40:36

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#7 2005-05-13 10:01:06

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#8 2005-05-13 10:04:57

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#11 2005-05-13 10:47:01

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#12 2005-05-13 10:50:40

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#14 2005-05-13 13:30:05

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#15 2005-05-13 13:37:55

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#16 2005-05-13 20:35:23

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#17 2005-05-15 22:53:18

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#18 2005-05-15 23:00:21

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