Number series – find the wrong term (identify the outlier). Sequence: 36, 54, 18, 27, 9, 18.5, 4.5

Introduction / Context:
Series may alternate two different operations. Here the task is to detect the alternating rule and find which term violates it.

Given Data / Assumptions:

• Series: 36, 54, 18, 27, 9, 18.5, 4.5
• Exactly one term is wrong.

Concept / Approach:
Check whether the sequence alternates between multiplying and dividing by a constant factor. Multiplying by 1.5 and then dividing by 3 is a common alternating pair because 1.5 and 1/3 are inverses over two steps in a ratio sense.

Step-by-Step Solution:

Verification / Alternative check:
Replace 18.5 with 13.5 and verify the full alternating pattern holds end to end. It does, confirming 18.5 is the outlier.

Why Other Options Are Wrong:

• 54, 18, 4.5: Each aligns with the alternating multiply by 1.5 and divide by 3 rule.

Common Pitfalls:
Comparing only differences instead of ratios can hide multiplicative patterns. Always test ratio-based operations in geometric series.

Final Answer:
18.5