A 7-digit base ten positive integer of the form ABCDEFG is called a modified hill number if the digits B, D and F satisfies: B = A + C (mod 10) , D = C + E (mod 10) and F= E + G (mod 10) (Each of the capital letters in bold denotes a digit from 0 to 9, whether same or different.)

Determine the probability that x is a modified hill number, given that x is a base ten positive integer chosen at random between 1000000 and 9999999 inclusively.

(In reply to answer by Dej Mar)

The 2145 figure is based on ignoring the "(mod 10)" notation and disallows such numbers as 2191219, where 1 = 2 + 9 (mod 10).

Posted by Charlie on 2011-03-10 11:48:35