Answer
a) 7 $\times 10^{-5}$ m
b) 7 $\times 10^{-8}$ km
Work Step by Step
(a) We can convert the thickness of hair in meters as
$1~\mu m=10^{-6}m$
$70~\mu m=70\times 10^{-6}$
$\implies 70\mu m=7.0\times 10^{-5}m$
(b) We know that
$1~m=10^{-3}Km$
$\implies 70\mu m=70\times 10^{-6}\times 10^{-3}Km$
$70~\mu m=7.0\times 10^{-8}K m$
