by mithunsam Tue Aug 30, 2011 12:45 pm
This problem has nothing to do with GMAT. But, still I would answer...
This can be solved in many ways. One of the easiest ways is to use logarithms.
First we need to find how many digits 7^35 has.
For that, we have to take log7^35 = 35log7 ~ 29.6 = 30 digits.
We have a maximum of 10 digits (0 to 9).
For minimum number of digits, one possibility is that each digit occur 3 times (3*10 = 30). However, since we are multiplying only by 7, last digit cannot be 0 (a 10 is required), 5(a five is required) etc. So, atleast one digit has to occur more than 3 times (that is 4 times).