Core ConceptRead this first — the foundation of the topic
Speed, Distance, and Time form the foundation of motion problems in SSC CGL. This topic appears in 2-3 questions per exam and requires strong formula application skills. Core Concept: Speed measures how fast an object moves. Distance is the path covered. Time is the duration taken. These three are linked by a simple relationship that forms the base of all calculations.
Formula BlockMemorise — at least one formula appears in every paper
• Speed = Distance/Time (S = D/T)
• Distance = Speed × Time (D = S × T)
• Time = Distance/Speed (T = D/S)
Unit Conversions (Critical for SSC):
• km/hr to m/s: Multiply by 5/18
• m/s to km/hr: Multiply by 18/5
• 1 km/hr = 5/18 m/s
Exam PatternsWhat examiners ask — read before attempting PYQs
Shortcut 1 - Unit Conversion Trick
To convert km/hr to m/s, multiply by 5/18
Remember
36 km/hr = 10 m/s (this is a standard conversion to memorize)
Shortcut 2 - Distance Formula Rearrangement
When speed increases by x%, new time = Original time × 100/(100+x)
When speed decreases by x%, new time = Original time × 100/(100-x)
Worked ExampleSolve this step-by-step before moving on
Convert to m/s
Speed in m/s = 60 × 5/18 = 300/18 = 16.67 m/s
Answer: 16.67 m/s
Worked Example 2:
A train running at 54 km/hr takes 20 seconds to cross a platform 200m long. Find the length of the train.
1
Step 1
Convert speed to m/s
54 km/hr = 54 × 5/18 = 15 m/s
2
Step 2
Find total distance covered
Distance = Speed × Time = 15 × 20 = 300m
3
Step 3
Find train length
Train length = Total distance - Platform length = 300 - 200 = 100m
Answer: 100 meters
Shortcut 3 - Relative Speed:
• Same direction: Relative speed = |S1 - S2|
• Opposite direction: Relative speed = S1 + S2
Most Common Trap (#1 Mistake):
Students forget unit conversions! SSC deliberately mixes km/hr and m/s in the same question. Always check units in options and convert accordingly. Questions asking for train crossing times usually need m/s, while car journey problems often use km/hr.
Another frequent error is confusing relative motion directions. When two objects move toward each other, add their speeds. When moving in the same direction, subtract speeds.
Time-based problems often trick students with percentage changes in speed. Remember: if speed increases by 25%, time decreases by 20% (not 25%). Use the reciprocal relationship carefully.
Practice identifying whether the question asks for train length, crossing time, or platform length. Each requires different approaches but uses the same core formula.
Key Points to Remember
Master formula: Speed = Distance/Time and its variations D = S × T and T = D/S
Unit conversion: km/hr to m/s multiply by 5/18, m/s to km/hr multiply by 18/5
Standard conversion: 36 km/hr = 10 m/s (memorize this)
Relative speed: same direction subtract speeds, opposite direction add speeds
Train problems: Total distance = Train length + Platform/Bridge length
Speed increase by x%: New time = Original time × 100/(100+x)
Speed decrease by x%: New time = Original time × 100/(100-x)
Always check units in answer options before solving
Average speed = Total distance/Total time (not average of individual speeds)
Time and speed are inversely proportional when distance is constant
Exam-Specific Tips
1 km/hr equals exactly 5/18 m/s
36 km/hr equals exactly 10 m/s
72 km/hr equals exactly 20 m/s
Average speed formula: Total distance divided by total time
Relative speed when objects move toward each other: Sum of individual speeds
Relative speed when objects move in same direction: Difference of individual speeds
When speed increases by 20%, time decreases by 16.67%
When speed decreases by 20%, time increases by 25%
Practice MCQs
Speed Distance Time — Practice Questions
17graded MCQs · easy to hard · full solution & trap analysis
A cyclist covers 180 metres in 9 seconds. What is his speed in m/s?
Practice 2easy
A runner completes 400 metres in 50 seconds. At this speed, how many metres will he cover in 2 minutes?
Practice 3easy
A train travels at 72 km/h. How far will it travel in 5 hours?
Practice 4easy
A man walks 150 metres in 30 seconds. How long will he take to walk 600 metres at the same speed?
Practice 5easy
A bus covers 360 km in 6 hours. If it travels at the same speed, how many kilometres will it cover in 9 hours?
Practice 6easy
A car travels 240 km in 4 hours. What is its average speed in km/h?
Practice 7medium
A cyclist covers 180 km in 5 hours. A car covers the same distance in 3 hours. What is the ratio of their speeds?
Practice 8medium
A man walks at 5 km/h and covers a certain distance in 8 hours. If he walks at 4 km/h, how much extra time will he need to cover the same distance?
Practice 9medium
Two runners start from the same point. Runner A runs at 12 km/h and Runner B runs at 8 km/h in the same direction. After how many hours will Runner A be 20 km ahead of Runner B?
Practice 10medium
A boat travels 48 km downstream in 3 hours and 48 km upstream in 6 hours. What is the speed of the boat in still water?
Practice 11medium
A car travels from City A to City B at 60 km/h and returns at 40 km/h. If the total journey takes 10 hours, what is the distance between the two cities?
Practice 12hard
A train travels from Station A to Station B, covering the first 120 km at 60 km/h and the next 180 km at 90 km/h. If the train halts for 30 minutes at an intermediate station, what is the average speed (in km/h) for the entire journey?
Practice 13hard
Two cyclists start simultaneously from the same point and travel in the same direction. Cyclist A travels at 24 km/h and Cyclist B travels at 32 km/h. After how many hours will Cyclist B be exactly 40 km ahead of Cyclist A?
Practice 14hard
A boat travels 60 km downstream in 3 hours and 60 km upstream in 5 hours. What is the speed of the current (in km/h)?
Practice 15hard
A car travels from City P to City Q at a speed of 50 km/h. On the return journey from Q to P, the car travels at 75 km/h. If the total time taken for the round trip is 10 hours, what is the distance between City P and City Q (in km)?
Practice 16hard
A runner covers a certain distance at 12 km/h and returns via the same route at 8 km/h. If the total time taken is 5 hours, what is the total distance covered (in km)?
Practice 17hard
Two trains start simultaneously from opposite ends of a 360 km track. Train A travels at 60 km/h and Train B travels at 90 km/h. After how many minutes will they meet?
60-Second Revision — Speed Distance Time
Formula: Speed = Distance/Time, Distance = Speed × Time, Time = Distance/Speed
Remember: 36 km/hr = 10 m/s for quick conversions
Unit conversion: km/hr to m/s multiply by 5/18
Trap: Always check if answer needs km/hr or m/s units
Relative speed: Add for opposite directions, subtract for same direction