Select the triad in which the numbers are related to each other in the same way as the numbers in the following triads. 8-17-35 23-47-95 (NOTE : Operations should be performed on the whole numbers, without breaking down the numbers into its constituent digits. E.g. 13 – Operations on 13 such as adding /deleting /multiplying etc., to 13 can be performed. Breaking down 13 into 1 and 3 and then performing mathematical operations on 1 and 3 is not allowed.)

Correct — B. Rule: next number = previous × 2 + 1, applied twice across the triad.

Check the given triads.
8 × 2 + 1 = 17, then 17 × 2 + 1 = 35
23 × 2 + 1 = 47, then 47 × 2 + 1 = 95

Now test option (b).
12 × 2 + 1 = 25
25 × 2 + 1 = 51

Both steps hold, so 12-25-51 is the matching triad.

Why the others are wrong

• (a)
  13-29-55 — 13 × 2 + 1 = 27, but the triad shows 29, and 29 × 2 + 1 = 59, not 55. Neither step follows the rule.
• (c)
  9-20-41 — The second step works (20 × 2 + 1 = 41), which makes this the tempting one, but the first fails: 9 × 2 + 1 = 19, not 20.
• (d)
  16-32-62 — 16 to 32 is a plain doubling with nothing added, and 32 × 2 + 1 = 65, not 62.

A number-triad analogy asks for one operation that turns each number into the next, and it must survive both steps.

Try doubling first. When the second number sits just above twice the first, the rest of the rule is usually a small constant: ×2+1 here, but ×2−1 and ×2+3 are built the same way.

The bracketed note — operate on whole numbers, never on their digits — is standard SSC wording. It narrows the search to arithmetic on 8, 17 and 35 as numbers, so nothing is gained by splitting 17 into 1 and 7.

Key facts

• 8 to 17 to 35 is ×2+1 at each step.
• 23 to 47 to 95 is ×2+1 at each step.
• 12 to 25 to 51 is ×2+1 at each step.

Common traps

• Accepting an option because its second step works and never testing the first
• Reading a near-double as a double, as with 16 to 32
• Breaking a number into its digits despite the question's note

No directly related past PYQ was found.