Problems 3, 5, 8 done

README.md

@@ -1,2 +1,3 @@
 DevPreWork01
 ============
+Here are some problems I solve for Startup Institute NY prework (Web Dev track).

problem03.rb

@@ -0,0 +1,19 @@
+require 'prime'
+
+def largest_prime(num)
+  # generate array of prime divisors
+  array = []
+  array = Prime.prime_division(num)
+  largest = 1
+  # look for the largest one
+  array.each do |entry|
+    if entry[0] >= largest
+      largest = entry[0]
+    end
+  end
+
+  largest
+end
+
+# puts largest_prime(13195)
+# puts largest_prime(600851475143)

problem05.rb

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+require 'prime'
+
+# helper function
+def comp(a,b)
+  a[1] = b[1] if a[1] < b[1]
+end
+
+# main function
+def smallest_multiple(a,b)
+
+  @arr = []
+  total = 1 
+
+  # helper that removes repeats
+  def help(i) 
+
+      if @arr == []
+        @arr << i        
+      else
+        foundIt=0
+
+        @arr.each do |x|
+          if x[0] == i[0]  
+            comp(x,i) 
+            foundIt=1
+            break
+          end
+        end
+
+        @arr << i if foundIt==0
+      end
+
+  end
+
+  # for each number in the range...
+  (a..b).each do |num|
+    temp = []
+    temp = Prime.prime_division(num)
+
+    temp.each do |i|
+      help(i)
+    end
+  end
+
+  # multiply all elements of array back into a total
+  total = Prime.int_from_prime_division(@arr)  
+  total
+end
+
+# puts smallest_multiple(1,20)

problem08.rb

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+
+def big_product(arr)  
+  product = 1
+  #iterate over the array
+
+
+  arr.each do |num|  
+    i = arr.index(num)
+
+     while (i <= (arr.length - 5)) do 
+           subproduct = 1     
+           subproduct = num * arr[i+1] * arr[i+2] * arr[i+3] * arr[i+4]  
+
+           if (subproduct >= product)
+                             product = subproduct
+          end  
+
+          i+=1
+
+    end
+
+
+  end
+
+  product
+
+end
+
+my_string = 
+"73167176531330624919225119674426574742355349194934
+96983520312774506326239578318016984801869478851843
+85861560789112949495459501737958331952853208805511
+12540698747158523863050715693290963295227443043557
+66896648950445244523161731856403098711121722383113
+62229893423380308135336276614282806444486645238749
+30358907296290491560440772390713810515859307960866
+70172427121883998797908792274921901699720888093776
+65727333001053367881220235421809751254540594752243
+52584907711670556013604839586446706324415722155397
+53697817977846174064955149290862569321978468622482
+83972241375657056057490261407972968652414535100474
+82166370484403199890008895243450658541227588666881
+16427171479924442928230863465674813919123162824586
+17866458359124566529476545682848912883142607690042
+24219022671055626321111109370544217506941658960408
+07198403850962455444362981230987879927244284909188
+84580156166097919133875499200524063689912560717606
+05886116467109405077541002256983155200055935729725
+71636269561882670428252483600823257530420752963450"
+
+my_string.gsub!(/(\n|\t|\r)/, ' ').gsub!(/(\s)/,"")
+
+my_array = my_string.chars.to_a.map {|num| num.to_i}
+
+
+# puts my_array[0].class
+# puts ( big_product(my_array) )