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RRB NTPC Boats & Streams

Study Material — 1 PYQs (2018–2018) · Concept Notes · Shortcuts

RRB NTPC Boats & Streams is a frequently tested subtopic — 1 previous year questions from 2018–2018 papers are included below with concept notes, key rules and shortcut tricks.

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2018–2018
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10 Key Points
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Previous Year Questions

RRB NTPC Boats & Streams — Past Exam Questions

1 questions from actual RRB NTPC papers · all shown free · click option to reveal solution

Exam Q 12018Previous Year Pattern

A boat travels 36 km downstream in 2 hours and returns the same distance upstream in 3 hours. What is the speed of the stream?

Concept Notes

Boats & Streams— Rules & Concept

Core ConceptRead this first — the foundation of the topic
Core Concept

Imagine walking on a moving escalator. If you walk in the same direction as the escalator, you move faster. If you walk against it, you move slower. Similarly, water current helps or hinders boat movement

Key Rules

Speed of boat in still water = (Downstream speed + Upstream speed) ÷ 2. Speed of current = (Downstream speed - Upstream speed) ÷ 2. Downstream speed = Boat speed + Stream speed. Upstream speed = Boat speed - Stream speed.

Formula BlockMemorise — at least one formula appears in every paper
• Downstream Speed = Speed in still water + Speed of stream
• Upstream Speed = Speed in still water - Speed of stream
• Speed in still water = (Downstream + Upstream) ÷ 2
• Speed of stream = (Downstream - Upstream) ÷ 2
• Time = Distance ÷ Speed
Exam PatternsWhat examiners ask — read before attempting PYQs

Questions typically ask for boat speed in still water, stream speed, time calculations, or distance problems. Common formats include round trips, meeting point problems, and comparative speed questions.

ShortcutsUse these to save 30–60 seconds per question

When distance is same upstream and downstream, use the harmonic mean formula: Average speed = (2 × Downstream speed × Upstream speed) ÷ (Downstream speed + Upstream speed).

Worked ExampleSolve this step-by-step before moving on
1
Step 1

Calculate speeds Downstream speed = 20 ÷ 2 = 10 km/hr Upstream speed = 12 ÷ 3 = 4 km/hr

2
Step 2

Apply formulas Boat speed in still water = (10 + 4) ÷ 2 = 7 km/hr Stream speed = (10 - 4) ÷ 2 = 3 km/hr Worked Example 2: A man can row 6 km/hr in still water. Stream speed is 2 km/hr. How long to travel 16 km downstream and return?

1
Step 1

Calculate effective speeds Downstream speed = 6 + 2 = 8 km/hr Upstream speed = 6 - 2 = 4 km/hr

2
Step 2

Calculate times Time downstream = 16 ÷ 8 = 2 hours Time upstream = 16 ÷ 4 = 4 hours Total time = 2 + 4 = 6 hours Trick for Round Trips: Total time = Distance × 2 × Boat speed ÷ (Boat speed² - Stream speed²)

Exam TrapsCommon mistakes students make — avoid these

Students often confuse downstream and upstream directions. Remember: downstream means 'with the flow' (faster), upstream means 'against the flow' (slower). Another trap is adding stream speed when calculating upstream speed instead of subtracting it.

Always check if your downstream speed is greater than upstream speed.

Key Points to Remember

  • Downstream speed = Boat speed + Stream speed (water helps movement)
  • Upstream speed = Boat speed - Stream speed (water opposes movement)
  • Boat speed in still water = (Downstream + Upstream speeds) ÷ 2
  • Stream speed = (Downstream - Upstream speeds) ÷ 2
  • Downstream speed is always greater than upstream speed
  • For same distance upstream and downstream, use harmonic mean for average speed
  • Round trip time = 2D × Boat speed ÷ (Boat speed² - Stream speed²)
  • If stream speed equals boat speed, upstream movement becomes impossible
  • Time upstream is always more than time downstream for same distance
  • When stream speed is zero, upstream speed equals downstream speed

Exam-Specific Tips

  • Downstream speed formula: Speed in still water + Stream speed
  • Upstream speed formula: Speed in still water - Stream speed
  • Speed in still water = (Downstream + Upstream) ÷ 2
  • Stream speed = (Downstream - Upstream) ÷ 2
  • Round trip average speed = (2 × Downstream × Upstream) ÷ (Downstream + Upstream)
  • If boat speed < stream speed, upstream movement is impossible
  • Time ratio upstream:downstream = Downstream speed:Upstream speed
  • For equal time upstream and downstream, distances are in ratio of speeds
Practice MCQs

Boats & Streams — Practice Questions

35graded MCQs · easy to hard · full solution & trap analysis · showing 20 of 35

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Practice 1easy

A man can row a boat at 6 km/h in still water. If he rows downstream for 2 hours and covers 20 km, what is the speed of the stream?

Practice 2easy

A boat's speed in still water is 12 km/h and the stream speed is 3 km/h. If the boat travels 90 km downstream, how much time does it take?

Practice 3easy

A man can row 30 km downstream in 2 hours. The speed of the stream is 4 km/h. What is the speed of the man in still water?

Practice 4easy

A boat's speed in still water is 10 km/h and the stream speed is 3 km/h. How long will it take the boat to travel 91 km upstream?

Practice 5easy

A boat covers 72 km upstream in 9 hours. If the stream speed is 1 km/h, what is the speed of the boat in still water?

Practice 6easy

A boat travels 48 km downstream in 3 hours. If the speed of the stream is 2 km/h, what is the speed of the boat in still water?

Practice 7easy

A man can row 30 km downstream in 5 hours and 20 km upstream in 5 hours. What is the speed of the stream?

Practice 8easy

A boat takes 4 hours to travel 60 km downstream and 6 hours to travel the same distance upstream. Find the speed of the boat in still water.

Practice 9easy

The speed of a boat in still water is 8 km/h. If the boat travels 36 km downstream in 3 hours, what is the speed of the stream?

Practice 10easy

A boat travels 48 km downstream in 3 hours. If the speed of the stream is 2 km/h, what is the speed of the boat in still water?

Practice 11easy

A boat's speed in still water is 10 km/h and the stream speed is 3 km/h. How long will it take the boat to travel 56 km upstream?

Practice 12easy

A boat travels 72 km upstream in 9 hours. If the boat's speed in still water is 10 km/h, what is the speed of the stream?

Practice 13easy

A boat takes 4 hours to travel 60 km downstream and 6 hours to travel the same distance upstream. What is the speed of the stream?

Practice 14easy

A boat takes 5 hours to cover 100 km downstream and 10 hours to cover the same distance upstream. What is the speed of the stream?

Practice 15medium

A man can row 30 km downstream in 3 hours and 24 km upstream in 4 hours. In still water, how much faster is the downstream journey compared to the upstream journey (in terms of speed)?

Practice 16medium

The speed of a boat in still water is 15 km/h and the speed of the stream is 3 km/h. How much time will the boat take to cover 72 km downstream and then return to the starting point?

Practice 17medium

The speed of a boat in still water is 15 km/h and the speed of the stream is 3 km/h. How much time will the boat take to travel 72 km downstream and then return to the starting point?

Practice 18medium

A boat can travel 35 km upstream in 5 hours. If the speed of the stream is 2 km/h, what distance can the boat cover downstream in 4 hours?

Practice 19medium

A man can row 30 km upstream in 5 hours. If the stream speed is 2 km/h, what is the speed of the man in still water?

Practice 20medium

A boat can travel 20 km upstream in the same time it travels 30 km downstream. If the speed of the stream is 5 km/h, find the speed of the boat in still water.

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60-Second Revision — Boats & Streams

  • Remember: Downstream = Boat + Stream, Upstream = Boat - Stream
  • Formula: Still water speed = (Down + Up) ÷ 2, Stream = (Down - Up) ÷ 2
  • Trap: Never add stream speed to upstream calculation
  • Quick check: Downstream speed > Upstream speed always
  • Round trips: Use harmonic mean for average speed calculation
  • Time relationship: More time upstream than downstream for same distance
  • Direction clarity: With current = Downstream, Against current = Upstream
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