how many different sequences of 4 digits possible if the first digit must be 3,4 or 5 and if the sequence may not end in 000? repetition of digits is allowed.

Answer 1

number of sequences starting with 3,4, or 5 without any restrictions at the end
= 3x10x10x10 = 3000
but we don't want the numbers 3000, 4000 and 5000

so the number of sequences as stated is
3000 - 3 = 2997