100^5 : 1000^2 = (10^2)^5 : (10^3)^2 = 10^(2*5) : 10^(3*2) = 10^10 : 10^6 = 10^(10-6) = 10^4 = 10 000.
100^5 : 1000^2 = (10^2)^5 : (10^3)^2 = 10^(2*5) : 10^(3*2) = 10^10 : 10^6 = 10^(10-6) = 10^4 = 10 000.