According to the United States Treasury Department, the U. S national debt was 1.815 x 10 to the 13th power dollars on September 30, 2015 . On September 29, 2005 , the national debt was 4.974 x 10 to the power of 12 dollars . Find the amount of Increase in the national debt from September of 2005 to september of 2015? Write a sentence describing the increase in the national debt from 2005 to 2015 using scientific notation and using standard form.