Official Guide Explanation:
Data Sufficiency #14

Background

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Solution and Metadata

Question: 14
Page: 274
Difficulty: 5 (Moderate)
Category 1: Word Problems > Rate Problems > Combined Rate
Category 2: Word Problems > Measurement Problems >

Explanation: Statement (1) is insufficient. It gives us the relationship between how long Car Y spent on the bridge and how long Car X spent. Car X spent one second less on the bridge than did Car Y. However, we don't know how long Car Y spent.

Statement (2) is also insufficient. Car Y traveled across the half - mile bridge at 30 miles per hour, which is equivalent to a rate of 1 mile per two minutes, or a half - mile per minute. So while Car Y spent 1 minute on the bridge, we're not told anything about Car X.

Taken together, the statements are sufficient. (2) gives us Car Y's time on the bridge, while (1) gives us the relationship between the two cars' times. Choice (C) is correct.

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