If a bicycle travels 100 miles with two tires on the road and one spare, assuming equal wear across all tires, how many miles of wear does each tire accumulate?

• A. 66.7 miles
• B. 50 miles
• C. 100 miles
• D. 33.3 miles

Answer: (A)

When there are three tires and only two are on the road at any given moment, the wear accumulated per mile comes from two tires, not one. So over 100 miles, the total wear across all tires is 2 × 100 = 200 miles of wear. If this wear is distributed equally among the three tires, each tire ends up with 200/3 ≈ 66.7 miles of wear. This matches the idea that the spare helps share the workload so that no single tire bears the full 100 miles of wear.