diff --git a/Problem03Module.rb b/Problem03Module.rb
new file mode 100644
index 0000000..4322de3
--- /dev/null
+++ b/Problem03Module.rb
@@ -0,0 +1,35 @@
+require "prime"
+
+module Problem03Module
+
+	def Problem03Module.factorize(input) 
+	    primeFactors = []
+		if Prime.prime?(input) || input == 1
+			primeFactors[0,0] = input
+			return primeFactors
+		else
+			Integer.each_prime(input-1) do |aPrime|
+				if input % aPrime == 0
+					primeFactors[0,0] = aPrime
+					return primeFactors.concat(factorize(input / aPrime))
+				end
+			end
+		end
+	end
+
+	def Problem03Module.main(args)
+		begin
+			inp = args.first.to_i
+			if inp <= 0
+				raise "Enter a non-zero positive number"
+			end
+			primeFactors = factorize(inp)
+			printf("Largest prime factor for %d is %d\n", inp, primeFactors.last)
+			return primeFactors.last
+		rescue StandardError
+			printf("Unexpected exception occured finding largest prime factor! ")
+			printf("Usage: ruby problem03.rb <number>\n")
+			return nil
+		end
+	end
+end
\ No newline at end of file
diff --git a/README.md b/README.md
index 4b4187d..b0dc4c7 100644
--- a/README.md
+++ b/README.md
@@ -1,2 +1,13 @@
 DevPreWork01
 ============
+Usage:
+
+Problem#3 - Largest prime factor
+ruby problem03.rb <integer>
+
+Problem#5 - Smallest multiple that is divisible by numbers 1..n
+ruby problem05.rb <integer>
+
+Problem#8 - Largest product in a series of X digits  
+ruby problem08.rb <series_length> <consecutive_digits>
+
diff --git a/problem03.rb b/problem03.rb
index e69de29..1e00b3a 100644
--- a/problem03.rb
+++ b/problem03.rb
@@ -0,0 +1,3 @@
+require_relative 'Problem03Module'
+
+Problem03Module.main(ARGV)
\ No newline at end of file
diff --git a/problem03_rspec.rb b/problem03_rspec.rb
new file mode 100644
index 0000000..9044eb7
--- /dev/null
+++ b/problem03_rspec.rb
@@ -0,0 +1,17 @@
+require_relative 'Problem03Module'
+
+describe 'largest prime factor' do
+	it 'finds 1 as largest prime factor for input of 1' do
+		expect(Problem03Module.main([1])).to eq(1)
+	end
+	it 'finds 2 as largest prime factor for input of 2' do
+		expect(Problem03Module.main([2])).to eq(2)
+	end
+	it 'finds 5 as largest prime factor for input of 100' do
+		expect(Problem03Module.main([100])).to eq(5)
+	end
+	it 'mocks and stubs' do
+		double('ClassX').class
+		print instance_double("ClassX", :pages => 250).class.pretty_print_instance_variables
+	end
+end
\ No newline at end of file
diff --git a/problem05.rb b/problem05.rb
index e69de29..64c48e2 100644
--- a/problem05.rb
+++ b/problem05.rb
@@ -0,0 +1,54 @@
+require "prime"
+
+def factorize(input) 
+
+    primeFactors = []
+
+	if Prime.prime?(input) || input == 1
+		primeFactors[0,0] = input
+		return primeFactors
+	else
+		Integer.each_prime(input-1) do |aPrime|
+			if input % aPrime == 0
+				primeFactors[0,0] = aPrime
+				return primeFactors.concat(factorize(input / aPrime))
+			end
+		end
+	end
+end
+
+begin
+	n = ARGV[0].to_i
+	if n <= 0
+		raise "Enter a number greater than 0"
+	end
+	factors = (1..n).to_a().inject([]) do |facs, num| 
+		facs << factorize(num) 
+		facs
+	end 
+	all_factors = factors.flatten.uniq
+	exp_hash = factors.inject({}) do |e_hash, f|
+		count_hash = all_factors.inject({}) do |c_hash, factor|
+			c_hash[factor] = f.count(factor) 
+			c_hash
+		end
+		count_hash.each_pair do |k, v|
+			if e_hash.has_key?(k)
+				e_hash[k] = (e_hash[k] < v) ? v : e_hash[k]
+			else
+				e_hash[k] = v
+			end
+		end
+		e_hash
+	end
+
+	multiple = exp_hash.inject(1) do |m, (k,v)|
+		m = m * (k ** v)
+		m
+	end
+	exp_hash.each_pair { |k,v| printf("%d^%d * ", k, v) }
+	printf(" = %d\n", multiple);
+rescue StandardError
+	printf("Unexpected exception occured finding smallest multiple that is divisible by numbers 1..n!\n")
+	printf("Usage: ruby problem05.rb <number>\n")
+end
diff --git a/problem08.rb b/problem08.rb
index e69de29..5dac842 100644
--- a/problem08.rb
+++ b/problem08.rb
@@ -0,0 +1,40 @@
+# generate random series of 1000 digits
+begin
+	series_len = ARGV[0].to_i
+	digits = ARGV[1].to_i
+	if series_len <= 0 || digits <= 0 || digits > series_len
+			raise "Enter a number greater than 0"
+	end
+	series = (1..series_len).inject("") do |s, i| 
+		s << (48 + Random.rand(10)).chr
+		s
+	end
+
+	printf("Randomly generated series of %d digits is [ %s ]\n", series_len, series)
+
+	# find the sequence
+	i = 0
+	numseq = series.split(//).map { |i| i.to_i }
+	
+	product_seq = greatest_product_seq = numseq[i...digits]
+	product = greatest_product = product_seq.inject(:*)
+
+	while i < series.length-digits
+		#printf("%d %d %s %d %d \n", i, i+digits, numseq[i...i+digits], product, greatest_product)	
+		i = i+1
+
+		product_seq = numseq[i...i+digits]
+		product = product_seq.inject(:*)
+		if product > greatest_product
+			greatest_product = product
+			greatest_product_seq = product_seq
+		end
+	end 
+
+	printf("Largest product in the above series of %d consecutive digits is %s\n", digits, greatest_product_seq)
+
+rescue StandardError
+	printf("Unexpected exception occured finding largest product in X length series of Y consecutive digits\n")
+	printf("Usage: ruby problem08.rb <series_length> <consecutive_digits_count>\n")
+
+end