Difficulty: Easy
Correct Answer: 84
Explanation:
Introduction / Context:
Concentric circles model a circular track. Inner circumference and uniform width allow computation of inner and then outer radius.
Given Data / Assumptions:
Concept / Approach:
For a circle, C = 2 * π * r. First find r_in from C_in, then r_out = r_in + w.
Step-by-Step Solution:
Verification / Alternative check:
Compute outer circumference to sense-check: 2 * π * 84 = 2 * (22/7) * 84 = 2 * 22 * 12 = 528 m (plausible given width 14 m).
Why Other Options Are Wrong:
44, 22, 33, 70 correspond to inner or unrelated radii; only 84 equals inner plus width.
Common Pitfalls:
Forgetting to add width to get outer radius or using diameter instead of radius in the formula.
Final Answer:
84
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