see its simple, lets consider we have n records in main table.as all records are stored in BLOCKS.
soln 3)
number of blocks in main table : (n/3)
number of block for index table (level 1): (n/10) (every element maps to index table)
#blocks to hold data and index file : n/3 + n/10= 13n/30.
soln 4)
no. of blocks in index table = n/10 (level 1)
at level 2 = n/102.........................
suppose we have k levels so,
we can say that we will have levels till n/10k =1
taking log and computing we get k = log10n answer.