Select the related number from the given alternatives. 23 : 35 :: 47 : ?

In a number analogy of the form a : b :: c : ?, the two numbers of the first pair are connected by a single fixed arithmetic rule (most commonly a constant difference or a constant ratio). The same rule, applied to the third number, produces the missing fourth number.

1. Find the relationship between the first pair: 35 - 23 = 12, so the second number is 12 more than the first number.

2. Apply the same rule to the second pair: the missing number must be 12 more than 47.

3. 47 + 12 = 59.

The relationship holds symmetrically: just as 35 - 23 = 12, checking 59 - 47 also gives 12, so the same fixed difference connects both pairs. Among the alternatives, only 59 preserves this exact difference.

Hence, the missing number is 59.