Final answer:
The growth of U.S. National Debt over four years is approximately 0.169.
Step-by-step explanation:
To calculate the growth of U.S. National Debt over four years using scientific notation, we can subtract the starting debt from the ending debt and divide the result by the starting debt. In this case, the starting debt is $18,581,234,768,000 and the ending debt is $21,694,000,000,000.
(21,694,000,000,000 - 18,581,234,768,000) / 18,581,234,768,000 = 0.1685
The growth of U.S. National Debt over four years is approximately 0.1685, which can be expressed in scientific notation as 1.69 x 10-1 or 0.169 with 2 decimal places.