Bonjour !
a) 2x10²x5 = 2x5x10² = 10x10²
a) 1x10¹x10³ = 10^4
b) 25x10^³ x 4 =25x4x10³ = 100x10³
b) 1x10^²x10^³ = 1x10^5
c) 20x10^6x50 = 20x50x10^6
c = 1000x10^6 = 1x10^³x10^6
c = 1x10^9
d) 10^4x2,5x10^7x4 = 4x2,5x4x10^7
d) 40x10^7 = 4x10^¹x10^7
d) 4x10^8
Bonne journee.