If 2 is added to each odd digit and 3 is subtracted from each even digit in the number 7843651, how many digits will appear more than once in the new number thus formed?

Given: 7843651

If 2 is added to each odd digit and 3 is subtracted from each even digit in the number.

7 (odd) → 7 + 2 = 9

8 (even) → 8 – 3 = 5

4 (even) → 4 – 3 = 1

3 (odd) → 3 + 2 = 5

6 (even) → 6 – 3 = 3

5 (odd) → 5 + 2 = 7

1 (odd) → 1 + 2 = 3

New number: 9 5 1 5 3 7 3

Digits appearing more than once = 5 and 3 → 2 digits

So, Two digits will appear more than once in the new number thus formed.

Thus, correct option is (b).