Answer: a) \(3.6\cdot10^9\)
Step-by-step explanation:
The given multiplication problem is
\((1.2\cdot10^{28})(3\cdot10^{-19})\)
First we open the parenthesis, and then multiply corresponding terms.
\(1.2\cdot10^{28}\cdot3\cdot10^{-19}\\=(1.2\cdot3)\cdot(10^{28}\cdot10^{-19})\\=3.6\cdot10^{28+(-19)}.....[\text{by using law of exponents }a^ma^n=a^{m+n}]\\=3.6\cdot10^{28-19}\\=3.6\cdot10^9\)
Thus, a) is the right answer.
