The diameter of Mercury is approximately 4.9×1034.9×103 kilometers. The diameter of Saturn is approximately 1.2×1051.2×105 kilometers. About how many times greater is the diameter of Saturn than the diameter of Mercury?

To get the difference between the two diameters, all you have to do is subtract the smaller diameter (Mercury) from the larger diameter (Saturn) as follows:

Difference between the two diameters =diameter of Saturn-diameter of Mercury
Difference between the two diameters = (1.2*10^5) - (4.9*10^3)
Difference between the two diameters = 115100 km