Number series – constant decrement: 72, 63, 54, 45, ? Identify the next term when each step decreases by the same amount.

Difficulty: Easy

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 = 36

Verification / 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.

Number series – constant decrement: 72, 63, 54, 45, ? Identify the next term when each step decreases by the same amount.

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