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Q:

A thief is noticed by a policeman from a distance of 200 m. The thief starts running and the policeman chases him. The thief and the policeman run at the rate of 10 km and 11 km per hour respectively. What is the distance between them after 6 minutes?

A) 100 m B) 150 m
C) 190 m D) 200 m

Answer:   A) 100 m



Explanation:

Relative speed of the thief and policeman  =  (11 – 10) km/hr = 1 km/hr

Distance covered in 6 minutes  = {\color{Blue} \left ( \frac{1}{60}\times 6 \right )} km   = {\color{Blue} \frac{1}{10}} km = 100 m

{\color{Blue} \therefore } Distance between the thief and policeman = (200 – 100) m = 100 m.

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
 
Answer & Explanation Answer: 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

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2 27
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
 
Answer & Explanation Answer: C) 5.76 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

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2 28
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
 
Answer & Explanation Answer: C) 60 kmph

Explanation:

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

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

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2 69
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
 
Answer & Explanation Answer: B) 3/4 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.

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1 76
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
 
Answer & Explanation Answer: A) 40 kms

Explanation:

Let the actual distance travelled be x km.
Then x/8=(x+20)/12
=> 12x = 8x + 160
=> 4x = 160
=> x = 40 km.

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2 69