PDA

View Full Version : A little maths problem for you

Pages : [1] 2 3 4

Unregistered
05-18-2002, 10:35 AM
The eggs in a basket doubled every minute. After an hour, the basket was full. When was the basket full to the half?

Hammer
05-18-2002, 10:48 AM
duh... that's a tough one :rolleyes: I won't answer, I'll leave it for others to think over for now! :D

golfinguy4
05-18-2002, 11:04 AM
Why does this sound like hw?

111011 minutes
Figure that out and u will get the answer.

Unregistered
05-18-2002, 11:24 AM
Well, let me put it this way; our maths teacher gave us the question, it took about 2-3 minutes till I solved it:D

People started with variables for the time increasing, and almost everyone said the answer was 11110 minutes.

tgm
05-18-2002, 11:27 AM
Too easy, but it did take me 59 minutes to figure it out.

Zewu
05-18-2002, 11:31 AM
Impossible. This thread was posted 05:35pm, you replied 06:27pm.

maes
05-18-2002, 11:54 AM
>> Impossible. This thread was posted 05:35pm, you replied 06:27pm.
hmm try looking at that post again. especialy the number. and compare it with golfinguy4 posts ;)

/*damn, should have wayted 5 min to post this*/

Dissata
05-18-2002, 02:39 PM
I think TGM is trying to hint at the answer. if it doubles, it is half full at 59 min, so when half the basket is full and then it is doubled you have two halves which eaquel a whole

I can't spell can I:)

Zewu
05-18-2002, 02:46 PM
Bingo!

Jet_Master
05-18-2002, 05:49 PM
olrite, you math masterminds, here is a similar problem for you:

A big water tank has a hole. Every hour, half of the water that is remaining leaks out. If the tank had 2000 L of water at 12:00 PM, what would be the exact time when all the water is gone?

Jet_Master
05-18-2002, 05:50 PM
I have another one, but i will save it until someone answers the first one. The next one is a bit harder... bit of a challenge.

Sorensen
05-18-2002, 05:54 PM
>A big water tank has a hole. Every hour, half of the water that is remaining leaks out. If the tank had 2000 L of water at 12:00 PM, what would be the exact time when all the water is gone?

I believe that would take an infinite amount of time (or until there was one water molecule left).

golfinguy4
05-18-2002, 08:05 PM
I second Sorensen's response

fyodor
05-18-2002, 08:36 PM
I have another one, but i will save it until someone answers the first one. The next one is a bit harder... bit of a challenge.

What grade are you in?
Anyways, here is my problem for you:)
Here is the definition you need

The function r(z) is equal to the sum of 1/(n^z), where n=1,2,3,...infinity. To those of you familiar with sigma notation (that funny Greek 'E'), you would have 'n=1' below the sigma, the infinity sign above the sigma, and 1/(n^z) to the right of the sigma. Here is a pathetic graphical representation.

infinity
---
\ 1/(n^z)=r(z)
/
---
n=1

So here is the problem:
When z is a complex number of the form z=a+it [i=sqrt(-1)], do all solutions to the equation r(z)=0 have a=0.5? (a=real part of z)
Constraint: candidate solutions must have a nonzero imaginary part ie, 't' != 0. Explain the rationale behind your answer.
Anybody have any ideas? ;)

golfinguy4
05-18-2002, 08:53 PM
Dude, what class is this?

Jet_Master
05-18-2002, 09:07 PM
wow!! i am just in grade 10. i dont get that, especially with that
"pathetic graphical representation" i have no idea.

anyway, that was an easy one.
this one is tricky:

on a very windy day, a snail is trying to climb a small hill.
this is the small hill:

/ \
/ \
a / \ b side a = 20 meters
/ \ side b = 20 meters
__/______c______\____ side c doesn't matter

the snail climbs 5m and then for sure a gust of wind comes and sweeps it 3m down. if it is 12:00 PM right now, what time will it be (to the closest hour) when the snail gets to the top or over it?

answer coming up after a few guesses.

Jet_Master
05-18-2002, 09:11 PM
d'oh!!!
my graphic design of the hilll did not work.
ok, here is another try (in words)

the side that the snail is climbing is 20 meters long (slope and all the other stuff included, so no calculations required)
the opposite side is also same length
the base length of the hill does not matter;

all you really need to know is that the snail needs to walk 20 meters to get to the top and with the wind... you know the question...

Jet_Master
05-18-2002, 09:13 PM
in graphic words:

a/\b

a is the distancesnail has to go (one side of the hill) and that is 20 meters

Nick
05-18-2002, 09:41 PM
People started with variables for the time increasing, and almost everyone said the answer was 11110 minutes.

Isn't that a bit too large considering at t=60 min the egg basket is full.
Consider this, let N = number of eggs in the basket, t = the time in minutes.
Then we have
N = 2^t and since at t=60 the basket is full
N_full = 2^60 we want to find t when N = N_full/2 so we have
2^59 = 2^t. And so t = 59 minutes. Ok you probably could figure it out mentally now.

Nutshell
05-18-2002, 10:43 PM
Maybe use code tags

/\
/ \
/ \
/ \
/ \

Commander
05-18-2002, 11:24 PM
assuming that the snail climbs 5m per hour (since it was not mentioned--i didn't c it)
I would say it's 10 pm

Hammer
05-19-2002, 12:32 AM
Originally posted by Nick

Isn't that a bit too large considering at t=60 min the egg basket is full.
Consider this, let N = number of eggs in the basket, t = the time in minutes.
Then we have
N = 2^t and since at t=60 the basket is full
N_full = 2^60 we want to find t when N = N_full/2 so we have
2^59 = 2^t. And so t = 59 minutes. Ok you probably could figure it out mentally now.
Nick, dont' you recognise a bunch of ones and zeros? :D

vasanth
05-19-2002, 07:18 AM
Why so much of complications.. It takes 59 minutes.. Sine half + half is full... Half has to double and that takes one minute to double to become full... So 60 - 1 is 59.

Jet_Master
05-19-2002, 07:45 AM
that was not even a hard problem... someone else try a guess at my second question... one guess is not enough.i will reveal the ans after 1-2 more guesses.

Commander
05-19-2002, 12:48 PM
1259 hrs

Commander
05-19-2002, 12:49 PM
0.000000000001115465465246565432165498465 mins

Commander
05-19-2002, 12:50 PM
look...2 more guesses...noe give me the damn answer!!!!!!:mad:

Nick
05-19-2002, 05:19 PM
Nick, dont' you recognise a bunch of ones and zeros?

Now I do :)

Jet_Master
05-19-2002, 05:20 PM
yea ok, have it your way. te answer is soming up in my next post.

(I am practising methods to keep a moron in suspense. and it is working so far)

Jet_Master
05-19-2002, 05:26 PM
allright here is the answer:

on a very windy day, a snail is trying to climb a small hill.
the side length of the hill is 20 meters long. the snail climbs 5m and then for sure a gust of wind comes and sweeps it 3m down. if it is 12:00 PM right now, what time will it be (to the closest hour) when the snail gets to the top or over it?

the answer is 9 hours.
at the end of:
1st hour: climbs 5, drops 3. therefore climbed 2.
2nd hour: climbs 5, drops 3. therefore climbed 2+2=4.
3rd hour: climbs 5, drops 3. therefore climbed 4+2=6.
4th hour: climbs 5, drops 3. therefore climbed 6+2=8.
5th hour: climbs 5, drops 3. therefore climbed 8+2=10.
6th hour: climbs 5, drops 3. therefore climbed 10+2=12.
7th hour: climbs 5, drops 3. therefore climbed 12+2=14.
8th hour: climbs 5, drops 3. therefore climbed 14+2=16.
9th hour: climbs 5. therefore total climbed 16+5=21. Now the snail is over the top and therefore will not be swept back 3m.

see, that was not so easy.

golfinguy4
05-19-2002, 05:28 PM
Sorry, but you didn't give us enough info to solve the problem. You never mentioned how long it took the snail to climb the 5m. That is why I could not help you.

golfinguy4
05-19-2002, 05:31 PM
Jet_Master, what math class was this from?

Jet_Master
05-19-2002, 06:56 PM
You never mentioned how long it took the snail to climb the 5m. That is why I could not help you.

Oh! Damn!!! I could have sworn that i said in one hour the snail climbs 5 m and drops 3m.... D'oh!! And no-one ever posted asking me that question.

Sorry, but you didn't give us enough info to solve the problem.
I wanted to give more time, but look back to page two, and you will see that commander was rushing too much. he had gone mad and was pestering me to give the answer.

Jet_Master, what math class was this from?
This was not from any math class- this one was just from me. by the way, i am in grade 10.

Commander
05-19-2002, 08:09 PM
Oh! Damn!!! I could have sworn that i said in one hour the snail climbs 5 m and drops 3m.... D'oh!! And no-one ever posted asking me that question.go to this post (http://www.cprogramming.com/cboard/showthread.php?s=&threadid=17985#post115362) --- here, I did mention that there was no time mentioned....read the posts more carefully next time.....

Jet_Master
05-19-2002, 08:59 PM
here, I did mention that there was no time mentioned....read the posts more carefully next time.....

this was your previous post:

assuming that the snail climbs 5m per hour (since it was not mentioned--i didn't c it)
I would say it's 10 pm

when you said "assuming that the snail climbs 5m per hour..." i thought i already said it because you guessed it correctly. but i did not see that it was not mentioned; i also make mistakes you ass! i am human afterall. ........ happens. i apologized, what more do you want.

Jet_Master
05-19-2002, 09:01 PM
oh, and commander, next time try providing a direct link, instead of just to the first page of the thread.

Jet_Master
05-19-2002, 09:11 PM
ok, try this math problem.
*Note: If you get a terrible headache doing this, dont sue me. I will not force you to do this.*

You are driving a bus from point A to point K. When you start, you have 15 people aboard. At point B, 3 get off, 6 get on. At point C, 3 get off, 5 get on. At point D, 5 get off,1 gets off. At point E, 8 get off, 4 get on. At point F, 5 get on. At point G, 3 get off, 4 get on. At point H,3 get off, 9 get on. At point I, 2 get off. At point J, 3 get off. When you get to point K, what is the name of the driver?

Commander
05-19-2002, 09:12 PM
that post was supposed to take you to the post I posted.....

Jet_Master
05-19-2002, 09:13 PM
shut up please. now leave that topic.

Commander
05-19-2002, 09:15 PM
by the way, iforgot to post something....
it's not my fault that ur comp can't recognize anchors or you tried to scroll down b4 the browser had time to take yo to that anchor or you stopped the transfer or something else

OxYgEn-22
05-19-2002, 09:27 PM
here is one that i found quite trickey..

I hear that Bill Gates actually used this at a conference of about 200 programmers who were applying to Micro\$oft.. only 3 got in or so:D

There are two rooms completly isolated from each other, there is no way you can see into the other room at all.... one room has 3 light switches and the other room has a light in it... it is your job to find out which of the 3 switches turns on the light in that room.....

you can only walk down to the other room (with the light) ONCE!! however, you can flip the switches as many times as you like for as long as you like.

anyone? if u know this dont post the answer just yet for those who do not know it!!!

-good luck!

Dual-Catfish
05-19-2002, 09:43 PM
Walk to the other Room, turn on Switches 1 and 2, leave them on for a few minutes.
Turn off switch 1 off, and switch 3 on.

Walk back into the other room, reach up, touch the light. If it's off, switch 1 turns it on. If it's on and warm, switch 2 turns it on. If it's on and cold, switch 3 is the one.

Here's one for ya:

A guy walks into a 7-11 store and selects four items to buy. The clerk at the counter informs the gentleman that the total cost of the four items is \$7.11. He was completely surprised that the cost was the same as the name of the store. The clerk informed the man that he simply multiplied the cost of each item and arrived at the total. The customer calmly informed the clerk that the items should be added and not multiplied. The clerk then added the items together and informed the customer that the total was still exactly \$7.11.

What are the exact costs of each item?

Jet_Master
05-20-2002, 05:26 AM
for this question, does each item cost have to be in two decimal points (example: 1.45) or can it go beyond two (example: 1.4532623345)? I need to know that. because if it has to be two decimal points sharp, the closest total i could get was
sum: 7.11
product: 7.115724

but you said it has to be exact.

A guy walks into a 7-11 store and selects four items to buy. The clerk at the counter informs the gentleman that the total cost of the four items is \$7.11. He was completely surprised that the cost was the same as the name of the store. The clerk informed the man that he simply multiplied the cost of each item and arrived at the total. The customer calmly informed the clerk that the items should be added and not multiplied. The clerk then added the items together and informed the customer that the total was still exactly \$7.11.

What are the exact costs of each item?

Dual-Catfish
05-20-2002, 08:29 AM
Yes, it has to be exact. (2 Decimal places) Hint: you can use programming for this :)

dbaryl
05-20-2002, 01:05 PM
In the post below, I will be going off of the assumption that every item being sold can be expressed as some integer in terms of cents, ie you CANNOT have a fraction of a penny for a price of an item. If that is incorrect to assume so, please do tell me and ignore the post below.

I know that it might be possible to have fractional prices (in cents), such as
3 for \$0.25In any case, taht is what I assume, if I'm wrong, I'm wrong, won't be the first time.

dbaryl
05-20-2002, 01:10 PM
[EDIT]Highlited in red is incorrect!
I pick A, B, C, and D to be prices for the items being sold (in cents). The product will look like this:
A * B * C * D = 711
(A * B * C) * D = 711
>> 711 % (A * B * C) == 0

What I mean by above is that EACH of the items bust be an INTEGER FACTOR of 711, in order to divide 711 cents by either of the prices and get an integer value in cents again. This is based on the assumption that the prices are integer values in cents, can't have a dicimal of a cent in price.

Now, the integer factors of 711 are: 1, 3, 9, 79 and 237.

This is the same as:

\$0.01, \$0.03, \$0.09, \$0.79 or \$2.37

Let's theorize that all items are priced below \$2.37, that is either \$0.01, \$0.03, \$0.09 or \$0.79. This would mean that you must be able to get a sum of \$7.11 out of 4 items that are \$0.79 or below, which is impossible. If only 1 item is \$2.37, then the other 3 must add to 7.11 = 2.37 = 4.74 >> impossible again with 3 items below \$1. So, at least 2 items must be priced at \$2.37 each, leaving other 2 to be: 7.11 - (2 * 2.37) = 2.37

As you can see, it's impossible to have 2 items priced \$0.01, \$0.03, \$0.09, \$0.79 or \$2.37 to add to \$2.37 without them being \$0 and \$2.37. Now, this again is impossible, because the product must be a non-zero value.

I see no solution for this probem.

Jet_Master
05-20-2002, 03:11 PM
YES!!! Ha Ha Ha!!!

This IS getting INTERESTING!!! Ha Ha Ha !!!

I LOVE this thread!!!

Jet_Master
05-20-2002, 03:14 PM
dbaryl, thanks a lot for the info you have provided. I WILL use all that to find any possible solution if possible. if not possible, i will not possibly find an answer that is possible and is correct. but if there is a possible answer, i possibly can find it! just wait for the possible; or for some, my accptance of the impossible.

(either way, i am sure that i have confused you by now)

Dual-Catfish
05-20-2002, 03:21 PM
There is an absolute answer... I once had a program written in C which calculated the answer(s) but I lost it when my HD crashed.

I know the values, but the program would be damn cool to have now :(

Jet_Master
05-20-2002, 03:29 PM
the closest i could get was:
the items cost \$1.00, \$2.91, \$1.94, \$1.26

the sum is \$7.11
but the product is \$7.113204 - when you round this up to two decimal points, i get: \$7.11!!

but, i didnot use programming. just my mind and a calculator.