Study the given pattern carefully and select the number that can replace the question ark (?) in it.
First row: 243, 162, 9
Second row: 108, 72, 6
Third row: 48, ?, 4
(NOTE: Operations should be performed on the whole numbers, without breaking own the numbers into its constituent digits. E.g. 13 - Operations on 13 such as dding / subtracting / multiplying etc. to 13 can be performed. Breaking down 13 into 1 nd 3 and then performing mathematical operations on 1 and 3 is not allowed)