Exercice 71 :
4900 = 4,9.10^3
12100 = 1,21.10^4
12700 = 1,27.10^4
6,8.10^3 = 6800
140000 = 1,4.10^5
1,21.10^5 = 121000
5,1.10^4 = 51000
4,85.10^4 = 48500
Exercice 72 :
A = 2400 x 30 000
A = 2,4.10^2 x 3.10^4
A = 7,2 x 10^(2+4)
A = 7,2.10^6
B = -6000 x 0,00003
B = -6.10^3 x 3.10^(-5)
B = (-6) x 3 x 10^(3-5)
B = -18.10^(-2)
B = -1,8.10^(-1)
C = 0,0005 x 0,004
C = 5.10(-4) x 4.10^(-3)
C = 5 x 4 x 10^(-4-3)
C = 20 x 10^(-7)
C = 2.10^(-6)
D = 72000 / 0,08
D = 7,2.10^4 / 8.10^(-2)
D = 7,2 / 8 x 10^4 / 10^(-2)
D = 7,2/8 x 10^(4+2)
D = 0,9.10^6
