2
Q:

# A person goes to his office at 1/3rd of the speed at which he returns from his office. If the average speed during the whole trip is 12 m /h . what is the speed of the person while he was going to his office?

 A) 10 B) 6 C) 8 D) can't be determined

Explanation:

u = k , v= 3k

$\inline&space;\therefore&space;\frac{2uv}{u+v}\:&space;\:&space;\Rightarrow&space;\frac{2\times&space;k\times&space;3k}{(k+3k)}=12$

$\inline&space;\Rightarrow&space;1.5k&space;=&space;12$

$\inline&space;\Rightarrow&space;k=8km/h$

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 30
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 30
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 71
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

Explanation:

Walking at 3/4th of usual rate implies that time taken would be 4/3th of the usual time. In other words, the time taken is 1/3rd more than his usual time

so 1/3rd of the usual time = 15min
or usual time = 3 x 15 = 45min = 45/60 hrs = 3/4 hrs.

1 81
Q:

If Hema walks at 12 km/hr instead of 8 km/hr, she would have walked 20 km more. The actual distance travelled by Hema is ?

 A) 40 kms B) 30 kms C) 46 kms D) 32 kms