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Q:

Shahrukh starts from Barabanki to Fatehpur , 1 hour after Ajay starts. Shahrukh meets Kajol 1.5 hours after Shahrukh starts. If the speed of Shahrukh is at least 20km/h faster than the speed of Kajol.

What is the minimum speed of Shahrukh to overtake Ajay, before he meets Kajol?

A) 30	B) 40
C) 60	D) None of these

Answer & Explanation Answer: D) None of these

Explanation:

Let t be the time after Kajol starts, when she meets Ajay, then

t = 300/(x+y)

This should be less than 2.5 or (x+y)>120

Since y= 3x/2 => y > 72

This (y>72) is greater than 67.5 km/h and hence Shahrukh will always overtake Ajay before he meets Kajol.

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Filed Under: Time and Distance

Q:

A boat sails 15 km of a river towards upstream in 5 hours. How long will it take to cover the same distance downstream, if the speed of current is one-fourth the speed of the boat in still water:

A) 1.8h	B) 3h
C) 4h	D) 5h

Answer & Explanation Answer: B) 3h

Explanation:

Upstream speed = B-S

Downstream speed = B+s

B-S = 15/5 = 3 km/h

Again B= 4S

Therefore B-S = 3= 3S

=> S = 1 and B= 4 km/h

Therefore B+S = 5km/h

Therefore, Time during downstream = 15/5 = 3h

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Filed Under: Boats and Streams

Q:

A motor boat takes 12 hours to go downstream and it takes 24 hours to return the same distance. what is the time taken by boat in still water?

A) 15 h	B) 16 h
C) 8 h	D) 20 h

Answer & Explanation Answer: B) 16 h

Explanation:

If t1 and t2 are the upstream and down stream times. Then time taken in still water is given by

$\frac{2 \times t 1 \times t 2}{t 1 + t 2} = \frac{2 \times 12 \times 24}{36} = 16 h$

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Filed Under: Boats and Streams

Q:

Two horses start trotting towards each other, one from A to B and another from B to A. They cross each other after one hour and the first horse reaches B, 5/6 hour before the second horse reaches A. If the distance between A and B is 50 km. what is the speed of the slower horse?

A) 30 km/h	B) 15 km/h
C) 25 km/h	D) 20 km/h

Answer & Explanation Answer: D) 20 km/h

Explanation:

If the speed of the faster horse be $f_{s}$ and that of slower horse be $s_{s}$ then

$f_{s} + s_{s} = \frac{50}{1} = 50$

and $\frac{50}{s_{s}} - \frac{50}{f_{s}} = \frac{5}{6}$

Now, you can go through options.

The speed of slower horse is 20km/h

Since, 20+30=50

and $\frac{50}{20} - \frac{50}{30} = \frac{5}{6}$

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Filed Under: Time and Distance

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

Answer & Explanation Answer: B) 150m

Explanation:

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

$x = (y + 3) \times \frac{5}{18} \times 36$ --------(1) and

$x = (y + 6) \times \frac{5}{18} \times 30$ ---------(2)

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

y = 12 km/h

Therefore, $x = (y + 3) \times \frac{5}{18} \times 36$ => x= 150 m

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Q:

If Deepesh had walked 20 km/h faster he woulh have saved 1 hour in the distance of 60km. what is the usual speed of Deepesh?

A) 100	B) 120
C) 150	D) None of these

Answer & Explanation Answer: A) 100

Explanation:

Let the original speed be x km/h, then

$\frac{600}{x} - \frac{600}{(x + 20)} = 1$

$\Rightarrow 600 (\frac{x + 20 - x}{x (x + 20)}) = 1$

$\Rightarrow x^{2} + 120 x - 12000 = 0$

$\Rightarrow (x - 120) (x - 100) = 0$

Therefore, original speed = 100km/h

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Filed Under: Time and Distance

Q:

A Person X started at 3 hours earlier at 40km/h from a place P, then another person Y followed him at 60km/h. Started his journey at 3 O'clock, afternoon. What is the diference in time when X was30 km ahead of Y and when Y was 30 km ahead of X?

A) 2h	B) 3h
C) 3.5h	D) 4.25h

Answer & Explanation Answer: B) 3h

Explanation:

Time ( when X was 30 km ahead of Y) = (120-30)/20 =4.5h

Time ( when Y was 30 km ahead of X) = (120+30)/20 = 7.5 h

Thus, required difference in time = 3h

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Filed Under: Time and Distance

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

Answer & Explanation Answer: C) 8

Explanation:

u = k , v= 3k

$∴ \frac{2 u v}{u + v} \Rightarrow \frac{2 \times k \times 3 k}{(k + 3 k)} = 12$ => k = 8km/h

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Filed Under: Time and Distance

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