## Problem 002

A place to air possible concerns or difficulties in understanding ProjectEuler problems. This forum is not meant to publish solutions. This forum is NOT meant to discuss solution methods or giving hints how a problem can be solved.
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newinkles
Posts: 1
Joined: Sun Mar 02, 2008 8:57 pm

### Problem 002

In the problem it says the sum of the even valued terms that do not exceed 4million. But the answer is the first term over 4 million. This might need to be reworded.

Nathan

hk
Posts: 10403
Joined: Sun Mar 26, 2006 9:34 am
Location: Haren, Netherlands

### Re: Problem 2

Why should the sum of the even valued fibonacci numbers less than 4 million not exceed 4 million?
The first fibonacci number that exceeds four million is 5702887. And that's not the correct answer.

So the individual terms to add must be less than 4 million, the sum does not need to be.

kinyel
Posts: 4
Joined: Thu Apr 10, 2008 6:05 pm

### problem 2 help please translate or example ...

Hello
I'm french (nobody's perfect... ) and my english is bad ...
and I don't understand really
"Find the sum of all the even-valued terms in the sequence which do not exceed four million."
what is "even valued" ? why not only "all terms" ?
please can someone translate in french, or (better ?) give me the wanted sum for the first 10 terms for example ...
( 1, 2, 3, 5, 8, 13, 21, 34, 55, 89 )
I can't solve this problem even if I've solve 20 others problems yet

thanks for help !

hk
Posts: 10403
Joined: Sun Mar 26, 2006 9:34 am
Location: Haren, Netherlands

### Re: problem 2 help please translate or example ...

even numbers are numbers divisible by 2.
So you are asked to sum the Fibonacci numbers less than 4 million that are divisible by 2.

kinyel
Posts: 4
Joined: Thu Apr 10, 2008 6:05 pm

### Re: problem 2 help please translate or example ...

thank you very, very much !

(never I think this and automatic translate don't give this ...)

dgiancaspro
Posts: 2
Joined: Sat Oct 25, 2008 9:58 pm

### Problem 2 -- What the heck ?

Sorry in advance for the long post ....
I completely understand the problem as it is stated. I wrote a quick brute force ruby program ... here it is ...

[snip]

I can't see what I'm doing wrong ... a nudge ... or a brick to the head ... in the right direction would be appreciated.

Thanks
Dave
Last edited by daniel.is.fischer on Sat Oct 25, 2008 10:24 pm, edited 1 time in total.

xan
Posts: 621
Joined: Fri Jul 27, 2007 11:43 pm
Location: North Carolina, USA
Contact:

### Re: Problem 2 -- What the heck ?

I don't know why your answer wasn't accepted. Maybe a copy/paste brought in some extra characters. If the problem persists, maybe an admin can figure out what the problem is.

daniel.is.fischer
Posts: 2400
Joined: Sun Sep 02, 2007 10:15 pm
Location: Bremen, Germany

### Re: Problem 2 -- What the heck ?

Whether it was a copy/paste slip or a server glitch, please try again and if that doesn't work, notify us.
Il faut respecter la montagne -- c'est pourquoi les gypa&egrave;tes sont l&agrave;.

dgiancaspro
Posts: 2
Joined: Sat Oct 25, 2008 9:58 pm

### Re: Problem 2 -- What the heck ?

Looks like it was a Copy/Paste glitch ... The one thing I didn't try was typing it in by hand. That's what I get for being lazy.
Sorry for the spoiler .... I'll remember that in the future ...

Thanks
Dave

hk
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Joined: Sun Mar 26, 2006 9:34 am
Location: Haren, Netherlands

### Re: Problem 2

Snipped out possible spoilers.
I don't think that makes for an efficient method: floats are slow compared to integers, moreover simple adding is much faster than multiplying or taking powers.
My prog based on the pdf runs in 0.003 milliseconds on a more than 4 years old computer using Delphi. (25 times as fast as yours)
Please do not post things like this again in the public part of this forum.

chinesefishmarket
Posts: 4
Joined: Fri Nov 28, 2008 7:43 pm

### Re: Problem 2

I'm having trouble with getting an answer for #2.
I have tried it for smaller numbers (limit 55) and I get 44 (34 + 8 + 2) for the answer. When I enter 4000000 as my limit, I get the wrong answer. Is there something I am missing about this problem?

ed_r
Posts: 1009
Joined: Sun Jul 29, 2007 9:57 am

### Re: Problem 2

Probably. Keep plugging away at it; you'll get there in the end. Good luck
(please note: this is not a hints forum!)
!647 = &8FDF4C

chinesefishmarket
Posts: 4
Joined: Fri Nov 28, 2008 7:43 pm

### Re: Problem 2

But if it works for a smaller number, it should work for a larger number as well.
I think the problem is my answers are coming out to be in the format X.XXXe+00X, because I tried problem 6 and it also said it was wrong.

So if my answer is 1.111e+003, the correct answer should be 1111 right?
(^ not an answer I got for either problem, just the same format).

stijn263
Posts: 1505
Joined: Sat Sep 15, 2007 10:57 pm
Location: Netherlands

### Re: Problem 2

try using integers instead of floats/doubles.

what programming language do you use?

chinesefishmarket
Posts: 4
Joined: Fri Nov 28, 2008 7:43 pm

### Re: Problem 2

stijn263 wrote:try using integers instead of floats/doubles.

what programming language do you use?
C++

chinesefishmarket
Posts: 4
Joined: Fri Nov 28, 2008 7:43 pm

### Re: Problem 2

chinesefishmarket wrote:
stijn263 wrote:try using integers instead of floats/doubles.

what programming language do you use?
C++
OK. Forcing everything to be int works out great.
Thank you.

stijn263
Posts: 1505
Joined: Sat Sep 15, 2007 10:57 pm
Location: Netherlands

### Re: Problem 2

Yup, you should avoid using doubles unless you have a good reason for using them. All projecteuler problems have answers smaller than 263, so using long long int will be sufficient.

If you're using cout to output your numbers, you can change the precision of the double output by setting: cout.precision(15);

Ints will always be fully shown.

phillyj
Posts: 2
Joined: Fri Oct 15, 2010 8:10 pm

### Problem 002

Hi, I looked over a previous post on #2 but I'm still confused. In my understanding, am I to find:

[1] the sum of all the even numbers and the sum should be less than or equal to 4 million?

[2] the sum of the even numbers under each of which is less than or equal to 4 million? In this case, the answer can be greater than 4 million.

Which way am I supposed to solve it?

Thank you

Susanne
Posts: 32
Joined: Sun Nov 08, 2009 7:39 am

### Re: Problem 002

It is case [2]. Each of the numbers must be smaller or equal 4 million.
Last edited by Susanne on Fri Oct 15, 2010 9:53 pm, edited 1 time in total.

phillyj
Posts: 2
Joined: Fri Oct 15, 2010 8:10 pm

### Re: Problem 002

I give up...for today. I thought I got the numbers but I keep getting it wrong. My code must be bad. I'm using matlab.