1, 3, 6, 10, 15, ?

Appeared in: SCTIMST Staff Nurse - 2015 (Set-A)

Explanation

The question presents a number series where the goal is to find the next term.
The pattern is based on the difference between consecutive numbers, which increases by 1 at each step (+2, +3, +4, +5).
The next logical difference to add is 6.
Adding 6 to the last number in the series, 15, gives the correct answer: 15 + 6 = 21.

Option A: This would be the result of adding 5 again (15 + 5 = 20), which fails to follow the pattern of the difference increasing by 1 at each step.
Option C: This would be the result of adding 7 (15 + 7 = 22). This incorrectly skips the next logical difference in the sequence, which is 6.
Option D: This result (15 + 8 = 23) does not follow any simple arithmetic or logical pattern based on the preceding numbers in the series.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Number Series as background academic context rather than a clinical decision trigger.
While not a clinical question, logical reasoning is a critical skill for nurses. It is used for interpreting patient data, prioritizing care, and troubleshooting equipment.
Problem-solving skills, like those tested in this question, are essential for making sound clinical judgments under pressure.
What if the series was 1, 4, 9, 16, 25? The pattern would be squaring the term number (1², 2², 3²...), and the next term would be 36 (6²). This demonstrates that different series have different underlying patterns to identify.

How to Approach the Question

First, carefully examine the given sequence of numbers: 1, 3, 6, 10, 15.
Calculate the difference between each consecutive pair of numbers to see if there is a simple pattern.
Step 1: 3 - 1 = 2
Step 2: 6 - 3 = 3
Step 3: 10 - 6 = 4
Step 4: 15 - 10 = 5

Concept Tested & Keywords

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Practise the full SCTIMST Staff Nurse - 2015 (Set-A)

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