diff --git a/problem05.rb b/problem05.rb
index e69de29..7a536d6 100644
--- a/problem05.rb
+++ b/problem05.rb
@@ -0,0 +1,27 @@
+def primes_up_to(num)
+  primes = [2]
+  i = 3
+  while i <= num
+    primes << i unless primes.any? {|element| i % element == 0}
+    i += 2
+  end
+  return primes
+end
+
+
+def smallest_prime_factor(num)
+  return 2 if num.even?
+  i = 3
+  while i <= num
+    return i if num%i==0
+    i += 2
+  end
+end
+
+def smallest_multiple(num)
+  arr = primes_up_to(num)
+  (2..num).to_a.each{|number| arr << smallest_prime_factor(number) unless arr.inject(:*)%number == 0}
+  arr.inject(:*)
+end
+
+p smallest_multiple(20)