Bonjour.
10 µm = 1,0.10^1 × 10^-6 m = 1,0.10^-5 m
=> 1 µm = 10^-6 m
900 Gm = 9,0.10^2 × 10^9 m = 9,0.10^11 m
=> 1 Gm = 10^9 m
0,00130 Mkm = 1,3.10^-3 × 10^6 km = 1,3.10^3 km = 1,3.10^3 × 10^3 m = 1,3.10^6 m
=> 1 Mm = 10^6 m
0,031 cm = 3,1.10^-2 × 10^-2 m = 3,1.10^-4 m
=> 1 cm = 10^-2 m
0,1 nm = 1,0.10^-1 × 10^-9 m = 1,0.10^-10 m
=> 1 nm = 10^-9 m
Bonne journée :)