Answer:
[tex]1.323 \times 10^{-2}[/tex]
Step-by-step explanation:
We need to find the product of 21 and (6.3 · 10-4). so let's multiply them.
[tex](21)(6.3 \times 10^{-4})[/tex]
[tex]=(21)(6.3) \times 10^{-4}[/tex]
[tex]=132.3 \times 10^{-4}[/tex]
[tex]=1.323 \times 10^{2} \times 10^{-4}[/tex]
[tex]=1.323 \times 10^{2} \times 10^{-4}[/tex]
[tex]=1.323 \times 10^{2-4}[/tex]
[tex]=1.323 \times 10^{-2}[/tex]
Hence correct answewr is 2nd choice.