Added the fifth problem from project Euler

Project Euler/Problem 5/problem5_sol1.rb

@@ -0,0 +1,23 @@
+# 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?
+
+
+# Euclid's algorithm for the greatest common divisor
+def gcd(a, b)
+  b.zero? ? a : gcd(b, a % b)
+end
+
+# Calculate the LCM using GCD
+def lcm(a, b)
+  (a * b) / gcd(a, b)
+end
+
+result = 1
+
+20.times do |i|
+  result = lcm(result, i + 1)
+end
+
+p result