6
Q:

# A train overtakes two girls who are walking in the  opposite direction in which the train  is going at the rate of 3 km/h and 6km/h and passes them completely in 36 seconds and 30 seconds respectively. The length of the train is:

 A) 120m B) 150m C) 125m D) None of these

Explanation:

Let the length of the train e x meter, and let the speed of train be y km/h, then

$\inline&space;x=\left&space;(&space;y+3&space;\right&space;)\frac{5}{18}\times&space;36&space;........(1)$

and        $\inline&space;x=\left&space;(&space;y+6\right&space;)\frac{5}{18}\times&space;30&space;........(2)$

From eq (1) and (2), we get

$\inline&space;(y+3)\times&space;36&space;=&space;(&space;y+6)\times&space;30$

y = 12 km/h

$\inline&space;\therefore$                 $\inline&space;x=(y+3)\times&space;\frac{5}{18}\times&space;36$

x= 150 m

Q:

Two persons start running simultaneously around a circular track of length 600 m from the same point at speeds of 25 kmph and 35 kmph. When will they meet for the first time any where on the track  ?

 A) 54 sec B) 36 sec C) 72 sec D) 11 sec

Explanation:

Time taken to meet the first time = length of track/relative speed

Given the length of the track is 600 m

The relative speed = 25 + 35 = 60 kmph = 60 x 5/18 m

Therefore Time = $\inline \fn_jvn \frac{600}{(25+35)\frac{5}{18}}$  = 600/60 x (18/5) = 36 sec.

0 3
Q:

A boy can swim in still water at 4.5 km/h, but takes twice as long to swim upstream than downstream. The speed of the stream is ?

 A) 1.8 kmph B) 2 kmph C) 2.2 kmph D) 1.5 kmph

Explanation:

Speed of Boy is B = 4.5 kmph

Let the speed of the stream is S = x kmph

Then speed in Down Stream = 4.5 + x

speed in Up Stream = 4.5 - x

As the distance is same,

=> 4.5 + x = (4.5 - x)2

=> 4.5 + x = 9 -2x

3x = 4.5

x = 1.5 kmph

2 44
Q:

A man can row 6 kmph in still water. When the river is running at 1.2 kmph, it takes him 1 hour to row to a place and back. What is the total distance traveled by the man ?

 A) 4.58 kms B) 6.35 kms C) 5.76 kms D) 5.24 kms

Explanation:

Speed in still water = 6 kmph

Stream speed = 1.2 kmph

Down stream  = 7.2 kmph

Up Stream = 4.8 kmph

x/7.2 + x/4.8 = 1

x = 2.88

Total Distance  = 2.88 x 2 = 5.76 kms

2 39
Q:

A person travels from K to L a speed of 50 km/hr and returns by increasing his speed by 50%. What is his average speed for both the trips ?

 A) 55 kmph B) 58 kmph C) 60 kmph D) 66 kmph

Explanation:

Speed on return trip = 150% of 50 = 75 km/hr.

Average speed = (2 x 50 x 75)/(50 + 75) = 60 km/hr.

2 78
Q:

Running 3/4th of his usual rate, a man is 15min late. Find his usual time in hours  ?

 A) 2/3 hrs B) 3/4 hrs C) 1/3 hrs D) 1/4 hrs