What we see: a yes or no Data Sufficiency question. Did Karen's speed ever go above 650 miles per hour at any moment of the flight?
Step 1. Notice what kind of speed the question asks about.
What we see: "ever exceed" means her top speed at any moment, not her average speed.
What it means: distance and time can only ever give us an average speed. An average does not tell us the highest speed.
What we do and why: keep that in mind, because it decides the whole question.
Step 2. Each statement alone.
What we see: statement 1 gives only the distance, 3,000 miles. Statement 2 gives only the time, 5 hours.
What it means: with only one of them we cannot even find her average speed.
What we do and why: each one alone is not enough.
Step 3. Both statements together.
What we see: 3,000 miles in 5 hours.
What it means: her average speed was \(3000 \div 5 = 600\) miles per hour.
What we do and why: test two flights that both average 600. Flight one: she flies 600 miles per hour the whole way, so she never goes above 650. The answer is no. Flight two: she flies slowly while climbing and landing, and 700 miles per hour in the middle, and it still averages 600. The answer is yes. Both flights fit the facts, so we cannot tell.
The trap: picking C because 600 is below 650. An average below 650 does not stop her from going faster than 650 for part of the flight.
Takeaway: Distance and time give only an average speed. A question about a highest or lowest speed at some moment needs more than an average.
Answer: E
