This GMAT DS train question is confusing me a bit — not sure which statement is actually needed here. Can someone explain?

Question

During a certain bicycle ride, was Sherry’s average speed faster than 24 kilometers per hour? (1 kilometer = 1,000 meters) .

1. Sherry’s average speed during the bicycle ride was faster than 7 meters per second.

2. Sherry’s average speed during the bicycle ride was slower than 8 meters per second.

S Raghav · Accepted Answer

This is a unit conversion question disguised as a speed comparison. First, convert 24 km/hr into meters per second. That&rsquo;s 24,000 meters divided by 3,600 seconds, which equals 6⅔ meters per second.
Now check the statements. Statement 1 says Sherry&rsquo;s speed was faster than 7 m/s. Since 7 is greater than 6⅔, that means her speed was definitely faster than 24 km/hr. So this statement is sufficient.
Statement 2 says her speed was slower than 8 m/s. But that leaves open multiple possibilities,  she could&rsquo;ve been going 7 (which is faster than 6⅔) or 5 (which is slower). So you can&rsquo;t say for sure whether her speed was over 24 km/hr or not. This one&rsquo;s not sufficient.
So only Statement 1 works. The answer is A.

Divakshi Arora · Answer

This question asks whether Sherry&rsquo;s average speed was faster than 24 kilometers per hour. To compare properly, first convert 24 km/h into meters per second, which comes out to 6⅔ meters per second.

Statement 1 says Sherry&rsquo;s speed was greater than 7 meters per second. Since 7 is more than 6⅔, this means her speed was definitely faster than 24 km/h. This statement is sufficient.
Statement 2 says her speed was less than 8 meters per second. That could mean she was going 7, which is fast enough, or 5, which is not. Since it allows for both outcomes, this statement is not sufficient.
Statement 2 leaves the result uncertain, so it doesn&rsquo;t help us reach a clear conclusion.
Only Statement 1 gives a definite yes to the original question.

Final answer is A. Only Statement 1 is sufficient.