2
Q:

# A man can row 9 km/h in still water. It takes him twice as long as to row down. Find the rate of stream of the river ?

Q:

The current of a stream at 1 kmph. A motor boat goes 35 km upstream and back to the starting point in 12 hours. The speed of the motor boat in still water is ?

 A) 8 kmph B) 6 kmph C) 7.5 kmph D) 5.5 kmph

Explanation:

Speed of the stream = 1
Motor boat speed in still water be = x kmph
Down Stream = x + 1 kmph
Up Stream = x - 1 kmph
[35/(x + 1)] + [35/(x - 1)] = 12
x = 6 kmph

1 24
Q:

A Bus is running at 9/10 of its own speed reached a place in 22 hours. How much time could be saved if the bus would run at its own speed ?

 A) 1.5 hrs B) 1.7 hrs C) 2.2 hrs D) 3.5 hrs

Explanation:

Let the original Speed be "s" kmph
And the usual time be "t" hrs
Given that if the bus is running at 9s/10 kmph the time is 22 hrs
=> [9s/10] x 22 = t x s
=> 99/5 = t
=> t = 19.8 hrs

Hence, if bus runs at its own speed, the time saved = 22 - 19.8 = 2.2 hrs.

1 30
Q:

How many seconds will a 800 meter long train moving with a speed of 63 km/hr take to cross a man walking with a speed of 3 km/hr in the direction of the train ?

 A) 48 B) 52 C) 38 D) 42

Explanation:

Here distance d = 800 mts
speed s = 63 - 3 = 60 kmph = 60 x 5/18 m/s
time t = $\inline \fn_jvn \small \frac{800x18}{60x5}$ = 48 sec.

1 24
Q:

P is faster than Q. P and Q each walk 24 km. The sum of their speeds is 7 km/hr and the sum of times taken by them is 14 hours. Then, P's speed is equal to ?

 A) 3 km/hr B) 4 km/hr C) 5 km/hr D) 6 km/hr

Explanation:

Let P's speed = x km/hr. Then, Q's speed = (7 - x) km/ hr.

So, 24/x + 24/(7 - x) = 14

$\fn_jvn \small x^{2}$ - 98x + 168 = 0

(x - 3)(x - 4) = 0 => x = 3 or 4.

Since, P is faster than Q,

so P's speed = 4 km/hr and Q's speed = 3 km/hr.

1 19
Q:

A man walks at a speed of 2 km/hr and runs at a speed of 6 km/hr. How much time will the man require to cover a distance of 20 1/2 km, if he completes half of the distance, i.e., (10 1/4) km on foot and the other half by running ?

 A) 12.4 hrs B) 11.9 hrs C) 10.7 hrs D) 9.9 hrs