The position of how many letters will remain unchanged if each of the letters in the word ‘NIGHTMARES’ is re-arranged in the English alphabetical order from left to right?

Correct — B. Write the word and its sorted form as two rows, then compare slot by slot.

NIGHTMARES: N I G H T M A R E S
Sorted: A E G H I M N R S T

1 N/A, 2 I/E, 3 G/G, 4 H/H, 5 T/I, 6 M/M, 7 A/N, 8 R/R, 9 E/S, 10 S/T

Positions 3, 4, 6 and 8 hold the same letter in both rows — four of them → option (b)

Why the others are wrong

• (a)
  One — One is an under-count. G in the 3rd slot is the easiest match to see, but H, M and R also survive the sort.
• (c)
  Two — Two is what you get from the adjacent pair G and H alone. M at position 6 and R at position 8 hold their places too.
• (d)
  Three — Three misses one match. The 8th slot is the one usually skipped: R stays exactly where it was.

This is bookkeeping, not reasoning. The only reliable method is to write the original letters in a row, write the alphabetical order directly beneath, and read down the columns.

Do the sort in one pass through the alphabet rather than by eye: A, E, G, H, I, M, N, R, S, T. Ten letters, all different, so nothing has to be tie-broken.

Then count the columns whose two letters agree. Counting in your head is where the answer moves by one.

Key facts

• NIGHTMARES in alphabetical order is A E G H I M N R S T.
• G, H, M and R occupy the same position before and after sorting.
• The word has ten letters and no letter repeats.

Common traps

• Sorting by eye instead of writing the two rows one under the other
• Stopping the comparison at the first mismatch
• Renumbering from the sorted row instead of the original word

No directly related past PYQ was found.