Boats and Streams - Aptitude Questions and Answers

Boats and Streams Questions and Answers

Learn and practice the chapter "Boats and Streams" with these solved Aptitude Questions and Answers. Each question in the topic is accompanied by a clear and easy explanation, formulae, shortcuts and tricks that help in understanding the concept.

Use of Boats and Streams Questions

The questions and examples given in this section will be useful to all the freshers, college students and engineering students preparing for placement tests or any competitive exam like MBA, CAT, MAT, SNAP, MHCET, XAT, NMAT, GATE, Bank exams - IBPS, SBI, RBI, RRB, SSB, SSC, UPSC etc.
1. A motorist can go downstream at 18 km/hr and upstream at 10 km/hr. Find the speed of the stream and the speed of the motorist in still waters.   

a. Motorist = 8 km/hr ; Stream = 28 km/hr
b. Motorist = 10 km/hr ; Stream = 5 km/hr
c. Motorist = 14 km/hr ; Stream = 4 km/hr
d. Motorist = 28 km/hr ; Stream = 8 km/hr

Answer: c. Motorist = 14 km/hr ; Stream = 4 km/hr

Explanation:

Man's/Boat's Speed = X
Stream/Current/River Speed = Y

∴ Downstream speed = X + Y
Upstream speed = X - Y


X+Y = 18 km/hr    and    X-Y = 10 km/hr

Adding them we get,
X+Y+X-Y = 28 km/hr

∴ X = 14 km/hr = Speed of Motorist
Y=18-14 = 4 km/hr = Speed of stream


2. A boatman rows his boat 48 km upstream and same distance downstream. The boat takes 12 hrs and 8 hrs to go upstream and downstream respectively. Find the speed of the boat in stagnant water and the speed of the stream respectively.

a. 4 km/hr ; 3 km/hr
b. 5 km/hr ; 1 km/hr
c. 6 km/hr ; 4 km/hr
d. 12 km/hr ; 6 km/hr
e. Cannot be determined

Answer: b. 5 km/hr ; 1 km/hr

Explanation:

Man's/Boat's Speed = X
Stream/Current/River Speed = Y

∴ Downstream speed = X + Y
Upstream speed = X - Y


Downstream Speed=Distance covered=48=6 km/hr
Time taken8

Upstream Speed=Distance covered=48=4 km/hr
Time taken12

X+Y = 6 km/hr    and    X-Y = 4 km/hr

Adding them we get,
X+Y+X-Y = 10 km/hr

∴ X=5 km/hr = Speed of Boat
Y=6-5 = 1 km/hr = Speed of stream





3. To swim upstream English Channel, a swimmer takes twice the time he takes to swim downstream. His speed in still water is 12km/hr. Find the speed of the English Channel.

a. 3 km/hr
b. 4 km/hr
c. 6 km/hr
d. 8 km/hr

Answer: b. 4 km/hr

Explanation:

Man's/Boat's Speed = X
Stream/Current/River Speed = Y

∴ Downstream speed = X + Y
Upstream speed = X - Y


X+Y = (12+Y) km/hr    and    X-Y = (12-Y) km/hr

Let time taken downstream be T hours.
∴ Upstream time = 2 x T = 2T hours

Distance is same
∴ D=D
∴ (12+Y) x T =  (12-Y) x 2T
∴ Y=4 km/hr = Speed of English Channel


4. Pramod's home and school are separated by a river. It takes him one hour to row to the school and come back. The river runs at a speed of 2.4 km/hr. Pramod's speed in still water is 12 km/hr. How far is the school from Pramod's home?

a. 3.6 km
b. 4.8 km
c. 5.76 km
d. 6.25 km

Answer: c. 5.76 km

Explanation:

Man's/Boat's Speed = X
Stream/Current/River Speed = Y

∴ Downstream speed = X + Y
Upstream speed = X - Y


X+Y = 12+2.4 = 14.4 km/hr    and    X-Y = 12-2.4 = 9.6 km/hr

Let distance be D km

Downstream time + Upstream time = 1 hour

Time=Distance covered
Speed

D+D=1
14.49.6

∴ D=5.76 km = The school is at this distance from Pramods's home.


5. While talking about a place to his friend Prashant said, "I could swim downstream to the place in 12 hours but while coming upstream it took 18 hours. The river was running at a speed of 6 km/hr." What is his speed in still water?

a. 12 km/hr
b. 24 km/hr
c. 30 km/hr
d. 36 km/hr

Answer: c. 30 km/hr

Explanation:

Man's/Boat's Speed = X
Stream/Current/River Speed = Y

∴ Downstream speed = X + Y
Upstream speed = X - Y


∴ X+Y = (X+6) km/hr    and    X-Y = (X-6) km/hr

Distance is same
∴ D=D
∴ (X+6) x 12 = (X-6) x 18
∴ X=30 km/hr = Speed of Prashant