Analogy (numbers) — “7 : 56 :: 9 : ?”. Detect the rule n*(n+1) and apply it to the second pair.

Introduction / Context:
Since 7 × 8 = 56, a natural rule is f(n) = n * (n + 1). Apply the same to n = 9.

Given Data / Assumptions:

• Use simple multiplicative progression.

Concept / Approach:
Compute 9 × 10.

Step-by-Step Solution:

Verification / Alternative check:
Competing rules (e.g., times 8) would give 72, which contradicts the first pair’s construction logic across n and n+1.

Why Other Options Are Wrong:
They are not equal to 9 × 10.

Common Pitfalls:
Applying a fixed multiplier rather than n + 1.

Final Answer:
90