diff --git a/ex9.1/d.cpp b/ex9.1/d.cpp
new file mode 100644
index 0000000..5b2d92d
--- /dev/null
+++ b/ex9.1/d.cpp
@@ -0,0 +1,82 @@
+#include <thread>
+#include <string>
+#include <iostream>
+#include <chrono>
+#include <vector>
+#include <functional>
+
+/*
+ * Compile with 'g++ -pthread a.cpp'
+ *
+ * Modifying an object
+ */
+
+using namespace std;
+
+/*
+ * This method will push the addition of the last two elements on the vector.
+ */
+void manipulate(vector<double>& v) {
+	int sleep = 2;
+	for ( int i = 0; i < 5; i++ )
+	{
+		double a = 0;
+
+		// Only use the last two elements
+		int j = 0;
+		for ( auto rit = v.rbegin() ; rit != v.rend(); ++rit )
+		{
+			if ( j > 1 )
+			{
+				break;
+			}
+
+			a += *rit;
+			++j;
+		}
+
+		v.push_back( a);
+		std::cout << "Updated Vector" << std::endl;
+
+		this_thread::sleep_for(std::chrono::seconds(sleep));
+	}
+}
+
+void display(vector<double>& v) {
+	int sleep = 1;
+	for ( int i = 0; i < 10; i++ )
+	{
+		std::cout << "Vector is now:" << std::endl;
+
+		std::cout << "{";
+		for ( int i = 0; i < v.size() ; i++ ) {
+			std::cout << v[i] << ", ";
+		}
+		std::cout << "}" << std::endl;
+		this_thread::sleep_for(std::chrono::seconds(sleep));
+	}
+}
+
+
+struct my_f {
+	vector<double>& v;
+
+	my_f(vector<double>& vv): v(vv) {};
+	void my_function() { manipulate(v); };
+};
+
+int main() {
+
+	vector<double> v { 1.1, 1.1 };
+	thread t {display, ref(v)};
+
+	my_f f{v};	
+	thread t2( &my_f::my_function, std::ref(f) );
+
+
+	// Run the threads
+	t.join();
+	t2.join();
+
+	return 0;
+}