Mauritania is 5.2 times larger than Senegal.
Area: 1,030,700 km2 World Factbook
Population: 3,516,806 (July 2014) World Factbook
Mauritania, officially the Islamic Republic of Mauritania, is a country in the Maghreb region of western North Africa. Wikipedia
Area: 196,722 km2 World Factbook
Population: 13,635,927 (July 2014) World Factbook
Senegal, officially the Republic of Senegal, is a country in West Africa. It is the westernmost country in the mainland of the Old World or Eurafrasia and owes its name to the Sénégal River that borders it to the east and north. Wikipedia