In a sequence of numbers, each number other than the first two is the sum of the two immediately preceding numbers from it. If the first two numbers in the sequence are 4 and 7, then the sixth number is

The problem describes a generalized Fibonacci sequence, which is a type of second-order linear recurrence relation where each term is the sum of the two preceding terms (Tₙ = Tₙ₋₁ + Tₙ₋₂). This additive sequence rule is historically notable, having been widely introduced to Western mathematics by Leonardo of Pisa (Fibonacci) in his 1202 book Liber Abaci.

Given the starting terms:

• 1st number (T₁) = 4
• 2nd number (T₂) = 7

Applying the sequence rule step-by-step:

• 3rd number (T₃) = 4 + 7 = 11
• 4th number (T₄) = 7 + 11 = 18
• 5th number (T₅) = 11 + 18 = 29
• 6th number (T₆) = 18 + 29 = 47

Therefore, the sixth number in the sequence is 47, making Option D correct.

Why the other options are wrong:

• Option A is incorrect because 29 represents the fifth number (T₅) in the sequence, not the required sixth term.
• Option B is incorrect; 37 is a mathematical miscalculation resulting from failing to add the immediately preceding valid terms (18 and 29).
• Option C is incorrect as 43 does not correspond to any correct summation of preceding terms in this specific recurrence relation.

Takeaway: For short mathematical sequences in aptitude tests, explicitly list and number each term sequentially (labeling them T₁ to Tₙ). This straightforward habit prevents common "off-by-one" mistakes, such as accidentally selecting the 5th term when the 6th is asked for.