Choose a correct option –
13 → 24 → 46 → ? → 123

Appeared in: NORCET 5 Prelims - Sept 2023 (Shift-1)

Explanation

The core logic of the series is that the difference between consecutive numbers increases by a constant value of 11.
The first difference is 24 - 13 = 11.
The second difference is 46 - 24 = 22 (which is 11 × 2).
Following this pattern, the third difference must be 33 (11 × 3).
Adding this difference to the last known term gives the missing number: 46 + 33 = 79.
To confirm, the next difference would be 44 (11 × 4), and 79 + 44 correctly equals 123, the final term in the series.

Option B: If the missing number were 68, the difference would be 68 - 46 = 22. This would mean the difference did not increase, breaking the established pattern of 11, 22, 33...
Option C: If the missing number were 55, the difference would be 55 - 46 = 9. This value does not fit the pattern of adding multiples of 11.
Option D: If the missing number were 78, the difference would be 78 - 46 = 32. This is very close to the correct difference of 33 but breaks the precise pattern of adding multiples of 11.

Visual 1: Flowchart: A visual flowchart showing the progression: 13 → (+11) → 24 → (+22) → 46 → (+33) → 79 → (+44) → 123. This helps to clearly visualize the increasing difference at each step.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Number Series Pattern Recognition as background academic context rather than a clinical decision trigger.
While not a clinical question, logical reasoning and pattern recognition are fundamental skills for nurses.
These skills are crucial for interpreting trends in patient vital signs, recognizing subtle changes in a patient's condition, and making quick, logical decisions in high-pressure situations.
What if the differences were 10, 20, 30? The underlying skill remains the same: identify the pattern (in this case, multiples of 10) and apply it to find the solution. This adaptability in problem-solving is key in nursing.

How to Approach the Question

First, analyze the relationship between the first few numbers in the series.
Calculate the difference between each consecutive pair of numbers (e.g., 24 - 13 = 11; 46 - 24 = 22).
Look for a pattern in the differences themselves. Here, the differences (11, 22) are multiples of 11.
Establish the rule for the pattern. The rule is to add the next multiple of 11 to the current term.
Apply this rule to find the missing number: The next difference is 33 (11 x 3), so 46 + 33 = 79.
Verify your answer by applying the rule one more time to see if it produces the final number in the series (79 + 44 = 123). This confirms your pattern is correct.

Concept Tested & Keywords

Q0BkMl2reSp5IxgCnU8cA7

Practise the full NORCET 5 Prelims - Sept 2023 (Shift-1)

Attempt every question from this paper in a timed mock, then review the full solution for each one.