Number series – constant decrement: 72, 63, 54, 45, ? Identify the next term when each step decreases by the same amount.
Verbal Reasoning
Number Series
Difficulty: Easy
Choose an option
Answer
Correct Answer: 36
Explanation
Introduction / Context:Here the series decreases linearly. Constant negative first differences are as common as constant positive ones and should be checked immediately.
Given Data / Assumptions:
- 72, 63, 54, 45, ?
- Uniform decrement suspected.
Concept / Approach:Compute a couple of differences: if they match, apply the same difference again to get the next term.
Step-by-Step Solution:
63 − 72 = −954 − 63 = −945 − 54 = −9Next: 45 − 9 = 36Verification / Alternative check:Working backward (36 + 9 = 45) supports the same constant step.
Why Other Options Are Wrong:
27, 81, 90 violate the −9 constant drop.Common Pitfalls:Confusing with ratio-based decreases; here the unit drop is fixed.
Final Answer:36