How many meaningful four-letter English words can be formed using the first, second, third, and fourth letters of the word "CAMERA" (when counted from left to right), using each letter only once in each word?

Correct — D.
Rule: fix the letters first, then test the arrangements for real words.

The first four letters of CAMERA are C, A, M, E.
Words using each of them once: CAME, MACE, ACME.

That is three words → option (d).

Why the others are wrong

• (a)
  One — One stops at CAME, the obvious word. MACE, a club or a spice, and ACME, the highest point, use the same four letters.
• (b)
  Four — Four needs a fourth word, and no other order of C, A, M and E is a standard English word. The count stops at three.
• (c)
  Two — Two leaves out one of CAME, MACE and ACME. All three are real words, each using C, A, M and E once.

Start by fixing the letters exactly. The first, second, third and fourth letters of CAMERA are C, A, M, E: four different letters, and every word must use all four once.

Then work through the arrangements one starting letter at a time. A gives ACME, C gives CAME, M gives MACE. None of the six orders starting with E is a word.

Key facts

• Letters used: C, A, M, E, the first four of CAMERA.
• Four different letters can be ordered 4! = 24 ways.
• Three of those orders are words: ACME, CAME, MACE.
• ACME means the highest point or peak.

Common traps

• Missing ACME because it is a less familiar word
• Counting abbreviations or proper names as meaningful English words

No directly related past PYQ was found.