Identify the pattern. 111X222, 222X333, 333X444, _________. Which fits next?

Correct — A.
Rule: both blocks rise by 111, and each term's right block becomes the next term's left block.

Left blocks: 111, 222, 333 → next 444
Right blocks: 222, 333, 444 → next 555

Next term: 444X555 → option (a).

Why the others are wrong

• (b)
  432X321 — 432X321 breaks the repeated-digit pattern. The left block must be 444 and the right block 555, while 432 and 321 count down instead of up.
• (c)
  345X654 — 345X654 uses mixed digits. Every term so far is two blocks of one repeated digit each, one digit apart, so the next is 444X555.
• (d)
  555X666 — 555X666 skips a step. It is the term after 444X555, since the left block must repeat the last right block, 444.

A pattern series can move along more than one track at once. Here each term is two three-digit blocks joined by X. Both blocks rise by 111 from term to term, and the right block of each term reappears as the left block of the next.

Both readings agree: after 333X444 comes 444X555.

Key facts

• 111, 222, 333, 444 and 555 are the first five multiples of 111.
• In this series the right block of one term is the left block of the next.
• The term after 333X444 is 444X555.

Common traps

• Jumping to 555X666 by starting the next term after the last right block instead of on it
• Looking for a digit-shuffling rule because options (b) and (c) mix their digits

No directly related past PYQ was found.