Trains, Boats & Streams
SSC GD Exam Preparation - Quantitative Aptitude
PART–1: TRAINS
1️⃣ Basic Formulas
Speed Formula
Speed = Distance / Time
2️⃣ Train Crossing a Pole
A pole has no length, so train must cover its own length.
Time = Length of Train / Speed
3️⃣ Train Crossing a Platform
Must cover its own length + platform length.
Time = (Train Length + Platform Length) / Speed
4️⃣ Two Trains Crossing Each Other
⦿ Opposite Direction
Relative Speed = S₁ + S₂
Time = (L₁ + L₂) / (S₁ + S₂)
⦿ Same Direction
Relative Speed = S₁ - S₂
Time = (L₁ + L₂) / (S₁ - S₂)
PART–2: BOATS & STREAMS
5️⃣ Basic Terms
- • Still Water Speed (Boat speed) = B
- • Stream Speed = S
- • Downstream = (B + S)
- • Upstream = (B – S)
6️⃣ Formulas
Downstream:
Speed_D = B + S
Upstream:
Speed_U = B - S
Finding Boat Speed (B):
B = (U + D) / 2
Finding Stream Speed (S):
S = (D - U) / 2
🧠 PART–3: Practice Questions (15 with Answers)
Test your trains, boats & streams concepts with these SSC GD level practice questions. Click on "View Answer" to check your understanding.
Q1. A train 150 m long crosses a pole in 15 sec. Find its speed.
View Answer
Speed = 150/15 = 10 m/s = 36 km/h
Q2. A 300 m train crosses a 200 m platform in 25 sec. Find speed.
View Answer
Distance = 300 + 200 = 500 m, Speed = 500/25 = 20 m/s = 72 km/h
Q3. Train A (200 m) and Train B (300 m) run in opposite directions at 54 km/h and 36 km/h. Time to cross?
View Answer
Relative speed = 54+36 = 90 km/h = 25 m/s, Distance = 200+300 = 500 m, Time = 500/25 = 20 sec
Q4. Two trains (150 m & 250 m) in same direction at 60 km/h & 42 km/h. Crossing time?
View Answer
Relative speed = 18 km/h = 5 m/s, Distance = 150+250 = 400 m, Time = 400/5 = 80 sec
Q5. A boat travels 30 km downstream in 3 hours. Find downstream speed.
View Answer
Speed = 30/3 = 10 km/h
Q6. Upstream speed = 6 km/h, downstream speed = 10 km/h. Find boat speed.
View Answer
B = (6+10)/2 = 8 km/h
Q7. Upstream = 8 km/h, Stream speed = 2 km/h. Find boat speed.
View Answer
B = U + S = 8 + 2 = 10 km/h
Q8. Boat speed = 12 km/h, stream = 3 km/h. Find upstream speed.
View Answer
U = B − S = 12 − 3 = 9 km/h
Q9. A boat covers 20 km upstream in 4 hours. Find upstream speed.
View Answer
U = 20/4 = 5 km/h
Q10. A train running at 72 km/h crosses a pole in 10 sec. Find length.
View Answer
72 km/h = 20 m/s, Length = 20 × 10 = 200 m
Q11. A 240 m train crosses a man in 12 sec. Find speed.
View Answer
Speed = 240/12 = 20 m/s = 72 km/h
Q12. Upstream speed = 4 km/h, downstream = 16 km/h. Find stream speed.
View Answer
S = (16 − 4)/2 = 6 km/h
Q13. A boat takes 2 hours for 20 km downstream. Find downstream speed.
View Answer
D = 20/2 = 10 km/h
Q14. If boat speed = 15 km/h and downstream speed = 20 km/h, find stream speed.
View Answer
S = D − B = 20 − 15 = 5 km/h
Q15. Train A (120 m) crosses Train B (180 m) in 12 sec. Relative speed = 25 m/s. Find direction.
View Answer
Distance = 300 m, Speed = 300/12 = 25 m/s, Matches given relative speed = opposite direction.
✅ SSC GD Exam Strategy
🟢 Remember train length calculations for poles vs platforms
🟢 Practice relative speed formulas for train crossings
🟢 Master boats & streams formulas (B = (U+D)/2, S = (D-U)/2)
🟢 Learn to quickly convert between km/h and m/s
🟢 Time yourself - aim for 45-60 seconds per question
You've completed Trains, Boats & Streams Concepts!
SSC GD Tip: Trains, Boats & Streams are high-scoring topics in the quantitative section. Focus on mastering the key formulas - for trains remember to add lengths when crossing platforms or other trains, and for boats remember the relationships between upstream, downstream, boat speed, and stream speed. Practice unit conversions and relative speed calculations as they frequently appear in exams. Regular practice with previous year SSC GD questions will build your speed and accuracy in solving these problems efficiently.
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