Project Euler

Multiples of 3 and 5

If we list all the natural numbers below 10 that are multiples of 3 or 5, we get 3, 5, 6 and 9. The sum of these multiples is 23.

Find the sum of all the multiples of 3 or 5 below 1000.


Even Fibonacci numbers

Each new term in the Fibonacci sequence is generated by adding the previous two terms. By starting with 1 and 2, the first 10 terms will be:

1, 2, 3, 5, 8, 13, 21, 34, 55, 89, …

By considering the terms in the Fibonacci sequence whose values do not exceed four million, find the sum of the even-valued terms.

this was fun, my first attempt was no successful, basically I create a code that would work for a small number of the series, and it work but when I plug the 4,000,000 well it kill the console, literally after few minutes it returns “kill” I guess that was the brute force approach and I pay dearly, the following code is the brute force and DO NOT plug it on your computer or you will pay for it, but it would be nice if you see it.

well that is what I got for creating arrays with millions of entries, jajaja,

now the second attempt, this time I had to do some research and took me time, but after some failures the following code is the one that work


Largest prime factor

The prime factors of 13195 are 5, 7, 13 and 29.

What is the largest prime factor of the number 600851475143 ?

This is one of those programs that need to be improve because I don’t think the code is efficient, it works, gets the job done but I will re-think this one latter and come with a better solution, in the mean time here is a working solution.


Largest palindrome product

A palindromic number reads the same both ways. The largest palindrome made from the product of two 2-digit numbers is 9009 = 91 × 99.

Find the largest palindrome made from the product of two 3-digit numbers.

 



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Posted December 15, 2016 by Edmundo in category "Ruby Examples