Study Material — 5 PYQs (2018–2020) · Concept Notes · Shortcuts
AFCAT Speed Distance Time is a frequently tested subtopic — 5 previous year questions from 2018–2020 papers are included below with concept notes, key rules and shortcut tricks.
5 questions from actual AFCAT papers · all shown free · click option to reveal solution
Exam Q 12018Previous Year Pattern
A train travels 240 km at a speed of 60 km/h. If the same train then travels 180 km at a speed of 45 km/h, what is the average speed for the entire journey?
Exam Q 22019Previous Year Pattern
A train travels 288 km in 4 hours. What is its speed in metres per second?
Exam Q 32019Previous Year Pattern
A train travels 240 km in 4 hours at constant speed. If it needs to cover an additional 180 km at the same speed, how much total time (in hours) will it take to complete the entire journey of 420 km?
Exam Q 42020Previous Year Pattern
A train travels 240 km in 4 hours at constant speed. If it needs to cover the same distance in 3 hours, by what percentage must its speed be increased?
Exam Q 52019Previous Year Pattern
A train travels from Station A to Station B at 60 km/h. On the return journey from B to A, it travels at 40 km/h. If the total time taken for the entire round trip is 10 hours, what is the distance between the two stations?
Concept Notes
Speed Distance Time— Rules & Concept
Core ConceptRead this first — the foundation of the topic
SPEED, DISTANCE AND TIME — COMPLETE EXAM GUIDE ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━
CORE CONCEPT ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━
Speed tells you how fast something moves. Distance is how far it travels. Time is how long it takes. These three are always connected. If you know any two, you can always find the third. Think of it this way: A car travels 120 km in 2 hours. Its speed is 60 km/h. Simple. That is the entire foundation of this topic.
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Formula BlockMemorise — at least one formula appears in every paper
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The three master formulas (all from one triangle):
Speed = Distance / Time
Distance = Speed x Time
Time = Distance / Speed
Unit Conversion (VERY important for SSC):
km/h to m/s → multiply by 5/18
m/s to km/h → multiply by 18/5
Memory HookRemember this — never confuse the two again
km/h is BIGGER than m/s, so to go from bigger to smaller, multiply by the smaller fraction (5/18).
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Key RulesCore rules you must know cold
Rule 2 — Average Speed
When a person travels the SAME distance at two different speeds (s1 and s2):
Average Speed = 2 x s1 x s2 / (s1 + s2)
WARNING: Do NOT simply add and divide by 2. That is wrong for equal distances
Rule 3 — Relative Speed
Two objects moving in the SAME direction → Relative Speed = (s1 - s2)
Two objects moving in OPPOSITE directions → Relative Speed = (s1 + s2)
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Exam PatternsWhat examiners ask — read before attempting PYQs
(What Gets Asked)
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SSC CGL almost always tests:
1. Average speed problems (equal distance, two speeds)
2. Unit conversion traps (km/h vs m/s)
3. A person is late or early — find original speed
4.
Two trains crossing each other
5. Meeting point problems
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SHORTCUTS AND TRICKS
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Shortcut 1 — Late and Early Trick:
A man is late by T1 minutes if he walks at s1 and early by T2 minutes if he walks at s2.
Distance = s1 x s2 x (T1 + T2) / (s2 - s1)
(Always make sure units match — convert minutes to hours if speed is in km/h)
Shortcut 2 — If speed is increased by a fraction:
New time = Old time x (original speed / new speed)
Time saved = Old time - New time
Example: Speed increases by 25% → New speed = 5/4 of old. New time = 4/5 of old. Time saved = 1/5 of original time.
Shortcut 3 — Two trains crossing a stationary object vs each other:
Crossing a pole/person: Time = Length of train / Speed of train
Crossing each other (opposite): Time = (L1 + L2) / (s1 + s2)
Crossing each other (same direction): Time = (L1 + L2) / (s1 - s2)
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Worked ExampleSolve this step-by-step before moving on
1
Step 1
Both distances are equal, so use the harmonic mean formula.
Average Speed = 2 x 40 x 60 / (40 + 60)
2
Step 2
Numerator = 2 x 40 x 60 = 4800
Denominator = 40 + 60 = 100
3
Step 3
Average Speed = 4800 / 100 = 48 km/h
Answer: 48 km/h
Note: Many students wrongly calculate (40 + 60) / 2 = 50 km/h. That is WRONG. Never use simple average for speed when distances are equal.
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WORKED EXAMPLE 2 — Late and Early
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Question: A student walks to school at 4 km/h and is late by 10 minutes. If he walks at 6 km/h, he reaches 5 minutes early. Find the distance to school.
1
Step 1
Use the Late and Early formula.
Distance = s1 x s2 x (T1 + T2) / (s2 - s1)
Here s1 = 4, s2 = 6, T1 = 10 min, T2 = 5 min
Distance = 4 x 6 x (1/4) / 2
= 24 x (1/4) / 2
= 6 / 2
= 3 km
Answer: Distance = 3 km
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Exam TrapsCommon mistakes students make — avoid these
— THE NUMBER ONE TRAP
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Students use simple average (s1 + s2) / 2 for average speed problems where EQUAL DISTANCES are covered at two different speeds. This is always WRONG. The correct formula is 2s1s2 / (s1 + s2).
Simple average only works when EQUAL TIME is spent at both speeds. SSC examiners set questions deliberately to trap students who use the wrong formula. Always ask yourself first: is the distance equal or is the time equal?
Key Points to Remember
Core Formula: Speed = Distance / Time. All three versions come from this one formula.
Unit Conversion: Multiply by 5/18 to convert km/h → m/s. Multiply by 18/5 to convert m/s → km/h.
Average Speed for EQUAL DISTANCES: Use 2s1s2 / (s1 + s2). Never use simple average.
Average Speed for EQUAL TIME: Use (s1 + s2) / 2. Simple average is correct ONLY in this case.
A man walks at 5 km/h. How much distance will he cover in 2 hours 24 minutes?
Practice 2easy
A bus covers 180 km in 3 hours. If it travels at the same speed, how many hours will it take to cover 420 km?
Practice 3easy
A runner completes 15 km in 1 hour 30 minutes. What is his speed in km/h?
Practice 4easy
A cyclist travels at 15 km/h for 2 hours, then at 20 km/h for 3 hours. What is the average speed for the entire journey?
Practice 5easy
A bus travels 180 km in 3 hours. If it increases its speed by 20%, how much distance will it cover in 5 hours at the new speed?
Practice 6easy
A train travels at 90 km/h. How long will it take to cover 360 km?
Practice 7easy
A runner covers 400 metres in 50 seconds. What is his speed in m/s?
Practice 8easy
A car travels 240 km in 4 hours. What is its average speed in km/h?
Practice 9easy
A cyclist covers 72 km in 6 hours. How far will he travel in 9 hours at the same speed?
Practice 10easy
A train travels at 90 km/h for 2 hours, then at 60 km/h for 3 hours. What is the average speed for the entire journey?
Practice 11easy
A car travels 240 km in 4 hours. What is its average speed in km/h?
Practice 12easy
A cyclist covers 150 km at a speed of 30 km/h. How much time does the journey take?
Practice 13easy
A man walks at 5 km/h and covers a distance in 8 hours. If he walks at 4 km/h, how much time will he take to cover the same distance?
Practice 14easy
A train travels at 90 km/h. How many metres does it cover in 10 seconds?
Practice 15easy
Two cities are 360 km apart. A bus travels from City A to City B at 60 km/h. How long does the journey take?
Practice 16easy
A train covers 450 km at a speed of 90 km/h. How much time does it take?
Practice 17easy
A cyclist covers 72 km in 8 hours. How much distance will he cover in 5 hours at the same speed?
Practice 18medium
A person travels from City A to City B at 40 km/h and returns at 60 km/h. If the total journey takes 10 hours, what is the distance between the two cities?
Practice 19medium
A boat travels 48 km upstream in 8 hours and 48 km downstream in 4 hours. What is the speed of the boat in still water?
Practice 20medium
A train travels 240 km in 4 hours at constant speed. If it needs to cover 360 km at the same speed, how much additional time (in hours) will it require beyond the initial 4 hours?
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