How many such pairs of digits are there in the given number ‘73951286’ each of…

In this class of reasoning question, every digit of the number is compared against the natural number series 0-9. For a pair of digits, find (a) how many digits sit between them as written in the given number, and (b) how many digits sit between their values when the series 0,1,2,...,9 is written out. A pair qualifies only when these two gaps are equal — the position gap in the number must match the value gap in the series.

1. 7 and 9: in the number, exactly one digit ('3') separates them (positions 1 and 3); in the series, exactly one digit ('8') lies between 7 and 9. The gaps match.

2. 7 and 2: in the number, four digits ('3, 9, 5, 1') separate them (positions 1 and 6); in the series, four digits ('3, 4, 5, 6') lie between 2 and 7. The gaps match.

3. 3 and 5: in the number, one digit ('9') separates them (positions 2 and 4); in the series, one digit ('4') lies between 3 and 5. The gaps match.

4. 3 and 8: in the number, four digits ('9, 5, 1, 2') separate them (positions 2 and 7); in the series, four digits ('4, 5, 6, 7') lie between 3 and 8. The gaps match.

5. 5 and 8: in the number, two digits ('1, 2') separate them (positions 4 and 7); in the series, two digits ('6, 7') lie between 5 and 8. The gaps match.

6. 1 and 2: in the number, the digits are adjacent (positions 5 and 6, zero digits between); in the series, 1 and 2 are also adjacent (zero digits between). The gaps match.

Testing every other digit combination in the number gives gaps that do not match. For instance, 7 and 6 are six digits apart in the number but adjacent (zero gap) in the series, and 5 and 1 are adjacent in the number but three digits apart in the series, so neither of these qualifies. That accounts for every pair; no combination beyond the six identified above satisfies the rule.

Six digit pairs satisfy the condition — well past four — so the correct count is 'more than four'.