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IBPS PO Quantitative Aptitude Boats and Streams Test 3

2431.The speed of a boat in still water is 25 kmph. If it can travel 10 km upstream in 1 hr, what time it would take to travel the same distance downstream?
22 minutes
30 minutes
40 minutes
15 minutes
Explanation:

Speed of boat in still water = 25 km/hr

Speed upstream $=\dfrac{10}{1}$ = 10 km/hr

Speed of the stream = (25-10) = 15 km/hr

Speed downstream = (25+15) = 40 km/hr

Time taken to travel 10 km downstream $=\dfrac{10}{40}\text{ hours} = \dfrac{10 \times 60}{40}$ = 15 minutes

2432.The speed of a boat in still water in 22 km/hr and the rate of current is 4 km/hr. The distance travelled downstream in 24 minutes is:
9.4 km
10.2 km
10.4 km
9.2 km
Explanation:

Speed downstream = (22 + 4) = 26 kmph

Time = 24 minutes $=\dfrac{24}{60}\text{ hour = }\dfrac{2}{5}\text{ hour}$

Distance travelled = Time × speed $=\dfrac{2}{5} \times 26$ = 10.4 km

2433.In one hour, a boat goes 14 km/hr along the stream and 8 km/hr against the stream. The speed of the boat in still water in km/hr is
12 km/hr
11 km/hr
10 km/hr
8 km/hr
Explanation:

Let speed of the boat in still water = a and speed of the stream = b

Then

a + b = 14

a - b = 8

Adding these two equations, we get 2a = 22

=> a = 11

ie,speed of boat in still water = 11 km/hr

2434.A motorboat, whose speed in 15 km/hr in still water goes 30 km downstream and comes back in a total of 4 hours 30 minutes. The speed of the stream in km/hr is:
4
5
6
10
Explanation:

Let the speed of the stream be $ x $ km/hr. Then,

Speed downstream = 15 + $ x $ km/hr,

Speed upstream = 15 - $ x $ km/hr.

$\therefore \dfrac{30}{(15 + x)} $+$ \dfrac{30}{(15 - x)} $= 4$ \dfrac{1}{2} $
$\Rightarrow$ $\dfrac{900}{(225 - x^2)}$ = $\dfrac{9}{2} $

$\Rightarrow$ 9$ x $2 = 225

$\Rightarrow x $2 = 25

$\Rightarrow x $ = 5 km/hr.

2435.The speed of a boat in still water in 15 km/hr and the rate of current is 3 km/hr. The distance travelled downstream in 12 minutes is:
1.2 km
1.8 km
2.4 km
3.6 km
Explanation:

Speed downstream = (15 + 3) kmph = 18 kmph.

Distance travelled =$ \left(18 \times\dfrac{12}{60} \right) $km = 3.6 km.
2446.The speed of a boat in still water is 15 km/hr and the rate of current is 3 km/hr. The distance travelled downstream in 24 minutes is
3.6 km
2.4 km
3.2 km
7.2 km
Explanation:

speed of a boat in still water = 15 km/hr

Speed of the current = 3 km/hr

Speed downstream = (15+3) = 18 km/hr

Distance travelled downstream in 24 minutes $=\dfrac{24}{60} \times 18 = \dfrac{2 \times 18}{5}\text{ = 7.2 km}$

2448.A boat goes 8 km upstream in 24 minutes. The speed of stream is 4 km/hr. The speed of boat in still water is:
25 km/hr
26 km/hr
22 km/hr
24 km/hr
Explanation:

Speed upstream $=\dfrac{8}{\left(\dfrac{24}{60}\right)}$ = 20 km/hr

Speed of the stream = 4 km/hr

speed of boat in still water = (20+4) = 24 km/hr

2449.A mans speed with the current is 15 km/hr and the speed of the current is 2.5 km/hr. The mans speed against the current is:
8.5 km/hr
9 km/hr
10 km/hr
12.5 km/hr
Explanation:

Mans rate in still water = (15 - 2.5) km/hr = 12.5 km/hr.

Mans rate against the current = (12.5 - 2.5) km/hr = 10 km/hr.

2451.Speed of a boat in standing water is 14 kmph and the speed of the stream is 1.2 kmph. A man rows to a place at a distance of 4864 km and comes back to the starting point. The total time taken by him is:
700 hours
350 hours
1400 hours
1010 hours
Explanation:

Speed downstream = (14 + 1.2) = 15.2 kmph

Speed upstream = (14 - 1.2) = 12.8 kmph

Total time taken $=\dfrac{4864}{15.2} + \dfrac{4864}{12.8}$ = 320 + 380 = 700 hours

2458.A boatman goes 2 km against the current of the stream in 1 hour and goes 1 km along the current in 10 minutes. How long will it take to go 5 km in stationary water?
40 minutes
1 hour
1 hr 15 min
1 hr 30 min
Explanation:
Rate downstream =$ \left(\dfrac{1}{10} \times 60\right) $km/hr = 6 km/hr.

Rate upstream = 2 km/hr.

Speed in still water =$ \dfrac{1}{2} $(6 + 2) km/hr = 4 km/hr.
$\therefore$ Required time =$ \left(\dfrac{5}{4} \right) $hrs = 1$ \dfrac{1}{4} $hrs = 1 hr 15 min.
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