The key concept here is Data Sufficiency with a unit conversion trap. Most people get this wrong not because the math is hard, but because they don't convert seconds to hours before applying the speed formula — and then they either eliminate the wrong airplane or incorrectly evaluate Statement 2.
Setup: Five airplanes with cruising speeds: A=480, B=600, C=650, D=520, E=550 mph.
Statement (1): Vernon's airplane takes less than 17 seconds to travel 3 miles.
This is a Speed = Distance ÷ Time problem, but the trap is the units mismatch — speed is in mph, but time is given in seconds.
Convert 17 seconds to hours: 17 seconds = 17/3600 hours.
For an airplane to travel 3 miles in less than 17 seconds:
Speed > 3 ÷ (17/3600) = 3 × (3600/17) ≈ 635.3 mph
Now check the five speeds against 635.3 mph:
- A (480): No
- B (600): No
- C (650): Yes ✓
- D (520): No
- E (550): No
Only airplane C exceeds 635.3 mph. Vernon must be on airplane C.
Statement (1) is SUFFICIENT.
Statement (2): Tracey's cruising speed is 20% lower than Vernon's.
"20% lower" means Tracey's speed = 0.8 × Vernon's speed. Check which pairs from our list satisfy this:
- 600 × 0.8 = 480 ✓ → Vernon on B, Tracey on A
- 650 × 0.8 = 520 ✓ → Vernon on C, Tracey on D
Two valid pairs exist. We cannot pin down which plane Vernon is on.
Statement (2) is NOT SUFFICIENT.
Answer: A
Common trap: Almost everyone loses Statement (1) because they compute "3 miles ÷ 17 seconds" without converting to mph — you get ~0.18, which means nothing when your speeds are in the hundreds. Always check your units in Distance-Rate-Time problems before plugging in. If speed is in mph, time must be in hours.
Takeaway: In DS Distance-Rate-Time problems, convert all units to the same system before comparing — a seconds-vs-hours mismatch will silently eliminate the right answer.