急 ! Logarithmic Function

10.
general form for seismic: magnitude = log [amplitude] + C where C is a constant
8 = log [A1] + C
6.5 = log [A2] + C
8 - 6.5 = {log [A1] + C} - {log [A2] + C}
1.5 = log [A1/A2]
10^1.5 = A1/A2]
A1/A2 = 31.6

11.
general form for soundness: Level = 10 log [Intensity/10^12]
50 = 10 log [Id/10^12]
L = 10 log [Ih/10^12]
50 - L = 10 log [Id/10^12] - 10 log [Ih/10^12]
50 - L = 10 log [Id/Ih]
50 - L = 10 log [10^(-6)]
50 - L = -60
L = 110dB

12.
55 = 10 log [It/10^12]
75 = 10 log [Is/10^12]
75 - 55 = 10 log [Is/10^12] - 10 log [It/10^12]
20 = 10 log [Is/It]
2 = log [Is/It]
10^2 = Is/It
Is/It = 100