Quantitative Aptitudeमात्रात्मक योग्यता · नाव और धारा

Boats and Streamsनाव और धारा questions and answersप्रश्न और उत्तर

Boats and streams is relative speed with the river as the moving partner.

Unlimitedअसीमित fresh questionsनए प्रश्न
Answersउत्तर always one tap awayहमेशा एक टैप दूर
1 subtopicउप-टॉपिक
SSC CGL ~1
IBPS PO ~1

Practice questions are in English for now.अभ्यास के प्रश्न अभी अंग्रेज़ी में हैं।

How boats and streams worksनाव और धारा को समझिए

Going downstream, the current helps: speed = boat + stream. Going upstream it opposes: speed = boat − stream.

Given downstream and upstream speeds, the boat’s speed in still water is their average and the stream’s speed is half their difference.

For a round trip over the same distance, time taken = d/(b + s) + d/(b − s). The upstream leg always takes longer, so the average speed of the round trip is less than the boat’s still-water speed.

Tricks that save timeसमय बचाने वाली ट्रिक्स

All tricks →सभी ट्रिक्स →

Each trick says when to use it, why it works and when it fails. Formula tricks are checked by code over their whole range.हर ट्रिक बताती है कि उसे कब इस्तेमाल करें, वह क्यों काम करती है और कब नहीं। सूत्र वाली ट्रिक्स को कोड से उनकी पूरी रेंज पर जाँचा गया है।

Formulaसूत्रRarely taughtकम सिखाई जाने वाली✓ Checked on 110 cases✓ 110 मामलों पर जाँची गई

Upstream takes k times as long → boat : stream = (k + 1) : (k − 1)

Use it when:कब इस्तेमाल करें: “A boat takes twice (or three times) as long to go upstream as downstream.”

Boat speed : stream speed = (k + 1) : (k − 1).

Exampleउदाहरण

Upstream takes 3 times as long; boat speed 12 km/h

→ Boat : stream = 4 : 2 → stream = 6 km/h

Why it works, and when it failsयह क्यों काम करती है, और कब नहीं

Why:क्यों: Same distance, so (b + s)/(b − s) = k, which rearranges to b/s = (k + 1)/(k − 1).

Limits:सीमाएँ: Same distance both ways; k > 1.

Solved examplesहल किए गए उदाहरण

Answers and full solutions are shown. Hide them to test yourself first.उत्तर और पूरे हल दिखाए गए हैं। पहले खुद को परखने के लिए इन्हें छिपाइए।

Example 1उदाहरण 1 · Boats and streams · Easyआसान
A boat on the Periyar has a speed of 8 km/h in still water. The stream flows at 1 km/h. How many hours will it take to go 54 km downstream?
1. 5 hours
2. 6 hours
3. 7 hours
4. 8 hours
Answer:उत्तर: 6 hours
1. Speed = 8 + 1 = 9 km/h.
2. Time = 54 ÷ 9 = 6 h.
Example 2उदाहरण 2 · Boats and streams · Mediumमध्यम
A boat goes 85 km downstream on the Ganga in 5 hours and 54 km upstream in 6 hours. Find the speed of the boat in still water (in km/h).
1. 10 kmph
2. 13 kmph
3. 14 kmph
4. 16 kmph
Answer:उत्तर: 13 kmph
1. Downstream = 17 km/h, upstream = 9 km/h.
2. Boat = (17 + 9)/2 = 13 km/h.
Example 3उदाहरण 3 · Boats and streams · Hardकठिन
A motorboat whose speed in still water is 12 km/h goes 32 km downstream on the Hooghly and comes back in a total of 6 hours. Find the speed of the stream (in km/h).
1. 2 kmph
2. 3 kmph
3. 4 kmph
4. 5 kmph
Answer:उत्तर: 4 kmph
1. 32/(12 + s) + 32/(12 − s) = 768/(144 − s²) = 6.
2. 144 − s² = 768 ÷ 6 = 128.
3. s² = 16, so s = 4 km/h.
4. Check: 32/16 + 32/8 = 2 + 4 = 6 h.
Example 4उदाहरण 4 · Boats and streams · Mediumमध्यम
A boat goes 40 km downstream on the Narmada in 4 hours and 12 km upstream in 6 hours. Find the speed of the boat in still water (in km/h).
1. 5 kmph
2. 6 kmph
3. 7 kmph
4. 8 kmph
Answer:उत्तर: 6 kmph
1. Downstream = 10 km/h, upstream = 2 km/h.
2. Boat = (10 + 2)/2 = 6 km/h.
Example 5उदाहरण 5 · Boats and streams · Mediumमध्यम
A boat goes 90 km downstream on the Brahmaputra in 5 hours and 50 km upstream in 5 hours. Find the speed of the stream (in km/h).
1. 2 kmph
2. 3 kmph
3. 4 kmph
4. 5 kmph
Answer:उत्तर: 4 kmph
1. Downstream = 18 km/h, upstream = 10 km/h.
2. Stream = (18 − 10)/2 = 4 km/h.
Example 6उदाहरण 6 · Boats and streams · Mediumमध्यम
A boat goes 80 km downstream on the Ganga in 5 hours and 18 km upstream in 3 hours. Find the speed of the boat in still water (in km/h).
1. 8 kmph
2. 9 kmph
3. 11 kmph
4. 12 kmph
Answer:उत्तर: 11 kmph
1. Downstream = 16 km/h, upstream = 6 km/h.
2. Boat = (16 + 6)/2 = 11 km/h.

Common mistakesआम गलतियाँ

Swapping upstream and downstream.
Forgetting to halve when finding the stream speed.

Frequently asked questionsअक्सर पूछे जाने वाले प्रश्न

What is the speed of a boat in still water?

Half the sum of its downstream and upstream speeds.

How do I find the speed of the current?

Half the difference of the downstream and upstream speeds.

Which is faster, upstream or downstream?

Downstream, because the current adds to the boat’s speed.