Given digits = 0, 1, 2, 3, 4, 5
Hence, 6-digit numbers formed by these digits = 6! = 6 × 5 × 4 × 3 × 2 × 1 = 720
If zero comes in first, then numbers becomes of 5-digit number then the 5-digit number formed is = 5!
= 5 × 4 × 3 × 2 × 1 = 120
Hence, the numbers that do not have zero in the begining are = 720 – 120 = 600.
