Hi All,
It looks like everyone's correctly answered the prompt, so I won't rehash any of that work here. Instead, I'm going to offer a bit more explanation as to why Fact 1 is insufficient. It's actually based on a "math truism", which in real simple terms is a "math fact that most people don't realize."
The Distance Formula is...
Distance = (Rate)(Time)
....and it's a formula that you'll likely use a couple of times on the Official GMAT (so it's worth knowing).
Fact 1 tells us that increasing the rate by 50% would lead to a time that is 2/3 of the original. Using the Distance Formula, we can prove that this occurs for ANY speed...
D = (R)(T)
Raising the Rate by 50% and decreasing the Time to 2/3 of the original time gives us...
(3/2)(R)(2/3)(T).
Since we're multiplying 'elements', we can put them in any order:
(3/2)(2/3)(R)(T)
(3/2)(2/3) = 6/6 = 1
So we have (1)(R)(T)
D = (R)(T)
In the end, the information in Fact 1 is NOT new information - it's a math fact when dealing with ANY speed and nothing more. Fact 1 is insufficient.
GMAT assassins aren't born, they're made,
Rich
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