According to the United States Treasury Department, the U.S. national debt was 1.815 x 10^13 dollars on September 30, 2015. On September 29,
2005, the national debt was 4.974 x 10^12 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.