Hi Kumar The question asks for 251st digit, we know that all the numbers in the given range are 4 digit numbers 248/4 =62. So we know that the required digit will be 3rd digit of the 63rd term in the given sequence. The given sequence is an AP with common difference 3, so 63rd term will be 1001 + 62*3 = 1001 +186 = 1187. So the required digit is 8. Hope that helps.