X = 0.abcdefghabcdefgh……………..

If unit digit is 1 then the next three places can be filled in 103 ways hence sum of all the digits at unit place

It also include numbers with period 1 and period 2

So sum of the numbers with period 8 = Total – Sum of the numbers with period 1, 2, 4

= 5 × 107 – 5 × 103 = 49995000