PlacementPrepA boat covers 30 km downstream in 2 hours and 21 km upstream in 3 hours. What is the speed of the boat in still water?
Solution
Downstream speed = 30/2 = 15; upstream = 21/3 = 7.
Boat speed = (15 + 7)/2 = 11 km/h.
Answer: (C) 11 km/h
Quantitative Aptitude · Work and motion
Boats and Streams: placement practice questions
30 moderate questions in the pattern of campus placement tests. Pick an option to check your answer, then open the step-by-step solution.
A man takes 3 times as long to row upstream as to row the same distance downstream. If the stream flows at 4 km/h, what is his speed in still water?
Solution
(b + 4) = 3(b − 4), so b(3 − 1) = 4(3 + 1).
b = 16/2 = 8 km/h.
Answer: (D) 8 km/h
A boat goes 13 km/h downstream and 7 km/h upstream. What is the speed of the stream?
Solution
Stream speed = (downstream − upstream)/2 = (13 − 7)/2 = 3 km/h.
Answer: (A) 3 km/h
A boat covers 108 km downstream in 4 hours and 22 km upstream in 2 hours. What is the speed of the boat in still water?
Solution
Downstream speed = 108/4 = 27; upstream = 22/2 = 11.
Boat speed = (27 + 11)/2 = 19 km/h.
Answer: (D) 19 km/h
A man takes 3 times as long to row upstream as to row the same distance downstream. If the stream flows at 3 km/h, what is his speed in still water?
Solution
(b + 3) = 3(b − 3), so b(3 − 1) = 3(3 + 1).
b = 12/2 = 6 km/h.
Answer: (B) 6 km/h
A boat goes 13 km/h downstream and 9 km/h upstream. What is the speed of the stream?
Solution
Stream speed = (downstream − upstream)/2 = (13 − 9)/2 = 2 km/h.
Answer: (C) 2 km/h
A boat covers 76 km downstream in 4 hours and 10 km upstream in 2 hours. What is the speed of the boat in still water?
Solution
Downstream speed = 76/4 = 19; upstream = 10/2 = 5.
Boat speed = (19 + 5)/2 = 12 km/h.
Answer: (D) 12 km/h
A boat covers 80 km downstream in 4 hours and 64 km upstream in 4 hours. What is the speed of the boat in still water?
Solution
Downstream speed = 80/4 = 20; upstream = 64/4 = 16.
Boat speed = (20 + 16)/2 = 18 km/h.
Answer: (A) 18 km/h
A man takes 3 times as long to row upstream as to row the same distance downstream. If the stream flows at 2 km/h, what is his speed in still water?
Solution
(b + 2) = 3(b − 2), so b(3 − 1) = 2(3 + 1).
b = 8/2 = 4 km/h.
Answer: (D) 4 km/h
A boat goes 24 km/h downstream and 4 km/h upstream. What is the speed of the stream?
Solution
Stream speed = (downstream − upstream)/2 = (24 − 4)/2 = 10 km/h.
Answer: (A) 10 km/h
A boat covers 57 km downstream in 3 hours and 12 km upstream in 4 hours. What is the speed of the boat in still water?
Solution
Downstream speed = 57/3 = 19; upstream = 12/4 = 3.
Boat speed = (19 + 3)/2 = 11 km/h.
Answer: (A) 11 km/h
A man takes 4 times as long to row upstream as to row the same distance downstream. If the stream flows at 3 km/h, what is his speed in still water?
Solution
(b + 3) = 4(b − 3), so b(4 − 1) = 3(4 + 1).
b = 15/3 = 5 km/h.
Answer: (C) 5 km/h
A boat goes 30 km/h downstream and 4 km/h upstream. What is the speed of the stream?
Solution
Stream speed = (downstream − upstream)/2 = (30 − 4)/2 = 13 km/h.
Answer: (A) 13 km/h
A boat covers 63 km downstream in 3 hours and 12 km upstream in 4 hours. What is the speed of the boat in still water?
Solution
Downstream speed = 63/3 = 21; upstream = 12/4 = 3.
Boat speed = (21 + 3)/2 = 12 km/h.
Answer: (C) 12 km/h
A boat goes 13 km/h downstream and 3 km/h upstream. What is the speed of the stream?
Solution
Stream speed = (downstream − upstream)/2 = (13 − 3)/2 = 5 km/h.
Answer: (D) 5 km/h
A boat covers 24 km downstream in 2 hours and 30 km upstream in 3 hours. What is the speed of the boat in still water?
Solution
Downstream speed = 24/2 = 12; upstream = 30/3 = 10.
Boat speed = (12 + 10)/2 = 11 km/h.
Answer: (D) 11 km/h
A boat (still-water speed 16 km/h) rows to a place and back in 6 hours. The stream flows at 4 km/h. How far is the place?
Solution
d/20 + d/12 = 6.
d × 32/240 = 6, so d = 45 km.
Answer: (C) 45 km
A boat goes 11 km/h downstream and 5 km/h upstream. What is the speed of the stream?
Solution
Stream speed = (downstream − upstream)/2 = (11 − 5)/2 = 3 km/h.
Answer: (C) 3 km/h
A boat goes 15 km/h downstream and 13 km/h upstream. What is the speed of the stream?
Solution
Stream speed = (downstream − upstream)/2 = (15 − 13)/2 = 1 km/h.
Answer: (C) 1 km/h
A boat's speed in still water is 8 km/h and the stream flows at 4 km/h. How long will it take to go 24 km downstream and come back?
Solution
Downstream time = 24/12 = 2 h; upstream = 24/4 = 6 h.
Total = 8 hours.
Answer: (C) 8 hours
A man takes 3 times as long to row upstream as to row the same distance downstream. If the stream flows at 1 km/h, what is his speed in still water?
Solution
(b + 1) = 3(b − 1), so b(3 − 1) = 1(3 + 1).
b = 4/2 = 2 km/h.
Answer: (B) 2 km/h
A boat's speed in still water is 8 km/h and the stream flows at 4 km/h. How long will it take to go 40 km downstream and come back?
Solution
Downstream time = 40/12 = 3 1/3 h; upstream = 40/4 = 10 h.
Total = 13 1/3 hours.
Answer: (D) 13 1/3 hours
A boat (still-water speed 18 km/h) rows to a place and back in 4 hours. The stream flows at 3 km/h. How far is the place?
Solution
d/21 + d/15 = 4.
d × 36/315 = 4, so d = 35 km.
Answer: (C) 35 km
A boat's speed in still water is 10 km/h and the stream flows at 2 km/h. How long will it take to go 30 km downstream and come back?
Solution
Downstream time = 30/12 = 2.5 h; upstream = 30/8 = 3.75 h.
Total = 6.25 hours.
Answer: (C) 6.25 hours
A man takes 2 times as long to row upstream as to row the same distance downstream. If the stream flows at 2 km/h, what is his speed in still water?
Solution
(b + 2) = 2(b − 2), so b(2 − 1) = 2(2 + 1).
b = 6/1 = 6 km/h.
Answer: (A) 6 km/h
A man takes 2 times as long to row upstream as to row the same distance downstream. If the stream flows at 3 km/h, what is his speed in still water?
Solution
(b + 3) = 2(b − 3), so b(2 − 1) = 3(2 + 1).
b = 9/1 = 9 km/h.
Answer: (D) 9 km/h
A boat (still-water speed 12 km/h) rows to a place and back in 6 hours. The stream flows at 2 km/h. How far is the place?
Solution
d/14 + d/10 = 6.
d × 24/140 = 6, so d = 35 km.
Answer: (D) 35 km
A boat (still-water speed 18 km/h) rows to a place and back in 8 hours. The stream flows at 3 km/h. How far is the place?
Solution
d/21 + d/15 = 8.
d × 36/315 = 8, so d = 70 km.
Answer: (A) 70 km
A boat (still-water speed 12 km/h) rows to a place and back in 3 hours. The stream flows at 4 km/h. How far is the place?
Solution
d/16 + d/8 = 3.
d × 24/128 = 3, so d = 16 km.
Answer: (C) 16 km
A boat's speed in still water is 10 km/h and the stream flows at 2 km/h. How long will it take to go 60 km downstream and come back?
Solution
Downstream time = 60/12 = 5 h; upstream = 60/8 = 7.5 h.
Total = 12.5 hours.
Answer: (D) 12.5 hours
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