diff --git a/README.md b/README.md index 4b4187d..c5283d9 100644 --- a/README.md +++ b/README.md @@ -1,2 +1,40 @@ + DevPreWork01 ============ + + +Problem #3 +
The prime factors of 13195 are 5, 7, 13 and 29. + +What is the largest prime factor of the number 600851475143 ?
+ +Problem #5 Smallest numebr +2520 is the smallest number that can be divided by each of the numbers from 1 to 10 without any remainder. + +What is the smallest positive number that is evenly divisible by all of the numbers from 1 to 20?
+ +Problem #8 largest product in a series + +Find the greatest product of five consecutive digits in the 1000-digit number.
+ +73167176531330624919225119674426574742355349194934 +96983520312774506326239578318016984801869478851843 +85861560789112949495459501737958331952853208805511 +12540698747158523863050715693290963295227443043557 +66896648950445244523161731856403098711121722383113 +62229893423380308135336276614282806444486645238749 +30358907296290491560440772390713810515859307960866 +70172427121883998797908792274921901699720888093776 +65727333001053367881220235421809751254540594752243 +52584907711670556013604839586446706324415722155397 +53697817977846174064955149290862569321978468622482 +83972241375657056057490261407972968652414535100474 +82166370484403199890008895243450658541227588666881 +16427171479924442928230863465674813919123162824586 +17866458359124566529476545682848912883142607690042 +24219022671055626321111109370544217506941658960408 +07198403850962455444362981230987879927244284909188 +84580156166097919133875499200524063689912560717606 +05886116467109405077541002256983155200055935729725 +71636269561882670428252483600823257530420752963450
+ diff --git a/problem01.rb b/problem01.rb new file mode 100644 index 0000000..729fa1a --- /dev/null +++ b/problem01.rb @@ -0,0 +1,13 @@ +#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. + +counter = [] + +(1..9).each do |x| + counter << x if (x%3 == 0 || x%5==0) + counter.inspect +end + +counter.inject { |sum, n| sum+n } +#or +#counter.reduce(:+) \ No newline at end of file diff --git a/problem03.rb b/problem03.rb index e69de29..904ccf8 100644 --- a/problem03.rb +++ b/problem03.rb @@ -0,0 +1,28 @@ + + + +#make method to check to see if number is prime + +def prime?(n) + (2..(n-1)).each { |x| return false if n % x == 0 } + true +end + +n =63 +array = [] +limit = 1 +x = 2 + +#make loop that checks to see what the prime numbers and shovels them into an empty array +while limit < n + if n % x == 0 && prime?(x) + array << x + limit *= x + end + x += 1 +end + +#array of prime numbers +array.inspect +#grab the last number in array +array.sort.last \ No newline at end of file diff --git a/problem04.rb b/problem04.rb new file mode 100644 index 0000000..56d0dfc --- /dev/null +++ b/problem04.rb @@ -0,0 +1,37 @@ +#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. + +#make a method to check if the number is a palindrome + +def palindrome?(n) + # convert n to a string + x = n.to_s + # get the length and divide by 2 + y = x.length/2 + # check to see if both sides equal + x[0..(y-1)] == x[-y..-1].reverse +end + + +def product_of_nums(n) + a = [] + max_sum = 0 + + 999.downto(100) do |i| + 999.downto(100) do |j| + sum = i * j + if (sum > max_sum); + if (palindrome?(sum)); + max_sum = sum + a << sum + break + end + end + end + end + return a.inspect; +end + +puts "answer: #{product_of_nums(3)}" + + diff --git a/problem05.rb b/problem05.rb index e69de29..3992e3c 100644 --- a/problem05.rb +++ b/problem05.rb @@ -0,0 +1,13 @@ +#2520 is the smallest number that can be divided by each of the numbers from 1 to 10 without any remainder. +#What is the smallest positive number that is evenly divisible by all of the numbers from 1 to 20? + +# Ruby docs least common multiple lcm + +num=(1..20).to_a +puts num.inject{ |x,n| x.lcm(n) } + +#find prime factors +def prime?(n) + (2..(n-1)).each {|x| return false if n % x == 0} + return true +end \ No newline at end of file