The series given below contains a sequence of numbers. Accordingly identify the incorrect combination.9 , 17 , 36 , 72 , 144 , 288

Correct — A.
Rule: each term is double the one before (×2).

9 × 2 = 18, but the series prints 17
18 × 2 = 36 ✓
36 × 2 = 72, 72 × 2 = 144, 144 × 2 = 288 ✓

One change, 17 → 18, repairs every link, so 17 is the wrong term → option (a).

Why the others are wrong

• (b)
  36 — 36 is 18 × 2, and 36 × 2 = 72. It fits the doubling on both sides, so the break lies before it, at 17.
• (c)
  72 — 72 is 36 × 2, and 72 × 2 = 144. It sits inside the unbroken run 36, 72, 144, 288.
• (d)
  288 — 288 is 144 × 2, the next doubling. The last term fits the rule the rest of the run sets.

Wrong-term items hide one misprint in a simple rule. Find the rule on the longest clean run, here 36, 72, 144, 288, each double the last, then walk it back to the start.

The settling test: one change should repair every link. Putting 18 for 17 gives 9, 18, 36, 72, 144, 288. Changing 9 instead cannot work, because 17 × 2 = 34, not 36.

Key facts

• The corrected series is 9, 18, 36, 72, 144, 288, doubling at each step.
• 17 breaks two links: 9 × 2 = 18, not 17, and 17 × 2 = 34, not 36.
• An interior wrong term breaks the links on both its sides, which is how 17 is located.

Common traps

• Blaming the first term, 9, though 17 × 2 = 34 still fails against 36
• Hunting a difference pattern (8, 19, 36, 72, 144) instead of testing a ratio

No directly related past PYQ was found.