Question 777926
First digit can be any of the 4 digits and hence be chosen in 4 ways.
Second digit also can be any of the 4 (since repeated digits are allowed).
Similarly, each of the 7 digits can be chosen in 4 ways.
Hence the total number of possible numbers = 4*4*4*4*4*4*4 = 4^7 = 16384.
Hope you got it :)