Use the rules of exponents (see Lesson 2) to simplify the following expressions. Represent the results in scientific notation.
1. \((3\times10^3)\times (4\times10^4)\)
2. \((5.1\times10^2)\times (4.2\times10^3)\)
3. \(\dfrac{5.925\times10^3}{2.45\times10^{-4}}\)
4. \(\dfrac{6.2\times10^3}{5\times10^5}\)
