The number of digits in N (positive integer) = floor($log_{10}$(N)) + 1. The integer part of $log_{10}$(N) is the characteristic. For N = 5^30: $log_{10}$(5^30) = 30*$log_{10}$(5) = 30*0.6990 = 20.97, so digits = 20 + 1 = 21. For finding leading zeros after decimal: if 0 < N < 1, the number of zeros immediately after the decimal point = |floor($log_{10}$(N))| - 1. Example: $\frac{1}{2}$^10 = 1/1024, log_{10}$$\frac{1}{1024} = -$log_{10}$(1024) = -3.010, floor = -4, zeros = 4 - 1 = 3 (i.e., 0.000976...). JEE gives $log_{10}$(2) and $log_{10}$(3) as data.