Speed, distance, and time problems appear often in aptitude exams. They all use one simple formula.
MCQ QuestionsQuantitative Aptitude
Speed, Distance and Time
Most errors come from skipping unit conversion, not from the formula itself
Core Formula
The base relationship
Speed = Distance ÷ Time
Rearrange for Distance = Speed × Time, or Time = Distance ÷ Speed
Unit Conversion
Match units first
km/h → m/s: × 5/18
m/s → km/h: multiply by 18/5 instead
Average Speed
Not a simple average
Total Distance ÷ Total Time
Never just average two different speeds directly
Relative Speed
Two moving objects
Add or subtract speeds
Add if moving toward each other, subtract if same direction
Must Know
- The core formula is: Speed = Distance / Time. Knowing any two values lets you find the third.
- To find distance, rearrange the formula: Distance = Speed × Time.
- To find time, rearrange it again: Time = Distance / Speed.
- Average speed for a whole journey is total distance divided by total time. This is not the same as simply averaging two different speeds.
- Units must match before you calculate. Convert km/h to m/s, or hours to minutes, before applying the formula.
Good to Know
- To convert km/h to m/s, multiply by 5/18. To convert m/s to km/h, multiply by 18/5.
- Relative speed applies when two objects move toward or away from each other. Add their speeds if moving toward each other, subtract if moving in the same direction.
- Train problems often add the train’s own length to the distance, since a train must fully clear a point or platform.
Test Yourself
Great to Know
- Most speed-distance-time errors come from skipping the unit-conversion step, not from misunderstanding the formula itself.
- Drawing a simple diagram of the journey helps avoid mistakes in relative-speed and two-train problems.
- These formulas also apply directly to real-world planning, like estimating travel time or fuel needs for a trip.
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