Data Sufficiency: Speed and Distance Sufficiency

Concept Explanation

Speed–distance DS items test whether distance, speed, or time can be found from given relations.

Standard Answer Choices

• A — Statement I alone is sufficient; Statement II alone is not.
• B — Statement II alone is sufficient; Statement I alone is not.
• C — Both together are sufficient, neither alone.
• D — Either statement alone is sufficient.
• E — Neither alone nor together is sufficient.

Speed/Distance DS Focus

Use Distance = Speed × Time. Convert km/hr and m/s when needed: m/s = (5/18) × km/hr.

DS Decision Flow

1. State exactly what must be determined (number, ratio, yes/no, or comparison).
2. Test Statement I alone—sufficient or insufficient?
3. Test Statement II alone—sufficient or insufficient?
4. If neither alone works, combine both statements.
5. Choose A–E based on sufficiency; never pick a value when data do not fix it uniquely.

Common Traps in Speed/Distance Problems

• Adding speeds instead of using harmonic mean for equal distances.
• Confusing average speed with average of two speeds.
• Mixing upstream/downstream without current speed.