A finite AP has common difference (-6). What will be the new common difference after writing it in reverse order?

Correct answer: (6)

The new common difference is 6, so D is correct. In the original finite AP, moving forward one place changes a term by d=−6. When the terms are written backward, moving forward in the reversed list means moving backward in the original list; therefore each change is the opposite, −d=−(−6)=6. A, −12, doubles the magnitude incorrectly. B, −6, is the old difference and does not account for reversal. C, 0, would mean all terms are equal, which is not true when the original difference is −6. D, 6, is the correct sign reversal. For example, 20,14,8 becomes 8,14,20, whose differences are 6. Memory cue: reversing a finite AP changes d to −d, not its magnitude to a new value.