80
using the ' law of exponents '
[tex]a^{m}[/tex] × [tex]a^{n}[/tex] = [tex]a^{( m + n)}[/tex]
2× [tex]10^{-3}[/tex] × 4 × [tex]10^{4}[/tex]
= ( 2 × 4 ) x ( [tex]10^{-3}[/tex] × [tex]10^{4}[/tex])
= 8 × [tex]10^{1}[/tex] = 8 × 10 = 80
