What should come in place of the question mark (?) in the given series?

672 670 666 660 652 ?

Appeared in: Bihar NHM CHO-2025

Explanation

The series follows a pattern of subtracting consecutive even numbers from each term.
The difference between the first and second term is 2 (672 - 2 = 670).
The difference between the second and third term is 4 (670 - 4 = 666).
This continues with a difference of 6 (666 - 6 = 660) and then 8 (660 - 8 = 652).
To find the next term, the next consecutive even number, 10, must be subtracted from the last term.
Therefore, 652 - 10 = 642.

Option A: This would result from subtracting 6 from 652. This is incorrect as it breaks the established pattern of subtracting progressively larger even numbers (the previous subtraction was 8).
Option B: This would mean subtracting 8 again (652 - 8 = 644). The pattern requires subtracting the next consecutive even number, not repeating the previous one.
Option C: This is the result of subtracting 12 from 652. This is incorrect because it skips the number 10 in the sequence of consecutive even numbers.

Visual 1: Flowchart - A flowchart illustrating the step-by-step subtraction of consecutive even numbers (2, 4, 6, 8, 10) from the starting number to arrive at the final answer.

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, this type of logical reasoning is a fundamental skill for nurses.
It reflects the ability to identify patterns and sequences, a skill used in monitoring patient vital signs for trends, titrating medications based on established protocols, and recognizing the progression of disease symptoms.
Strong analytical skills enable nurses to anticipate changes in a patient's condition and make proactive, sound clinical judgments.

How to Approach the Question

First, examine the relationship between the first two numbers: 672 and 670. The difference is -2.
Next, check the difference between the next pair: 670 and 666. The difference is -4.
Continue this process for the entire series: 666 to 660 is -6, and 660 to 652 is -8.
Identify the underlying rule: The series subtracts consecutive even numbers.
Apply this rule to find the missing term: The next even number after 8 is 10. Subtract 10 from the last known term (652).
Calculate the final answer: 652 - 10 = 642, and select the corresponding option.

Concept Tested & Keywords

Q3zv8HNKrxHHZhqKQHIT3N

Practise the full Bihar NHM CHO-2025

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