10
Q:

# The distance of the college and home of Rajeev is 80km. One day he was late by 1 hour than the normal time to leave for the college, so he increased his speed by 4km/h and thus he reached  to college  at the normal time. What is the changed (or increased) speed of Rajeev?

 A) 28 km/h B) 30 km/h C) 40 km/h D) 20 km/h

Explanation:

Let the normal speed be x km/h, then

$80x-80(x+4)=1$

$⇒$$x2+4x-320=0$

$⇒$x (x + 20) - 16 (x + 20) = 0

(x + 20 ) (x - 16) =0

x = 16 km/h

Therefore (x + 4) = 20 km/h

Therefore increased speed = 20 km/h

Q:

A bike runs at the speed of 35 km/h when not serviced and runs at 55 km/h, when serviced. After servicing the bike covers a certain distance in 5 h. How much approximate time will the bike take to cover the same distance when not serviced?

 A) 8 hrs B) 7.5 hrs C) 7 hrs D) 6.5 hrs

Explanation:

Given speed of the bike after servicing = 55 kmph

Time taken for travelling some distance at 55 kmph = 5 hrs

Then,

Distance = Speed x Time = 55 x 5 = 275 kms.

Now,

Speed of the bike before servicing = 35 kmph

Distance = 275 kms

Now, Time = Distance/Speed = 275/35 = 7.85 hrs =~ 8 hrs.

1 147
Q:

Akhil after travelling 50 km meets Raju who suggests him to go slower. He then proceeds at ¾ of his former speed and arrives at his destination 35 minutes late. Had the meeting occurred 24 km further Akhil would have reached its destination 25 minutes late. What is the initial speed of Akhil?

 A) 48 kmph B) 36 kmph C) 24 kmph D) 20 kmph

Explanation:

Let the initial speed of Akhil be '4p' kmph

Then speed after decrease in speed = '3p' kmph

We know that,

Change in speed == Change in time

According to the given data,

Hence, the initial speed of Akhil = 4p = 4 x 12 = 48 kmph.

1 326
Q:

A 200 m long train passes a motorcycler, running in the same direction at 12 km/hr, in 15 second and a jeep travelling in the same direction in 20 s. At what speed is the car travelling (length of both the motorcycler and jeep is negligible)?

 A) 36 kmph B) 32 kmph C) 29 kmph D) 24 kmph

Explanation:

Let the speed of the train be 'S' kmph

From the given data,

Distance = Length of train = D = 200 mts = 200 x 18/5 kms

Time = 10 sec

given speed of the motorcycler = 12 kmph

Relative speed as they are moving in the same direction = (S - 12) kmph

Hence, the speed of the train = S = 60 kmph

Now,

Let the speed of the jeep be 'x' kmph

Therefore, the speed of the jeep = x = 24 kmph.

1 319
Q:

Buses start from a bus terminal with a speed of 20 km/hr at intervals of 10 minutes. What is the speed of a man coming from the opposite direction towards the bus terminal if he meets the buses at intervals of 8 minutes?

 A) 5 kmph B) 6 kmph C) 7.5 kmph D) 8 kmph

Explanation:

Let p be the speed of man in kmph

According to the given data in the question,

Distance travelled by bus in 10 min with 20 kmph == Distance travelled by man in 8 min with (20 + p) kmph in opposite direction

=> 20 x 10/60 = 8/60 (20 + p)

=> 200 = 160 + 8p

=> p = 40/8 = 5 kmph.

2 237
Q:

With an average speed of 40 km/hr, a train reaches its destination in time. If it goes with an average speed of 35 km/hr, it is late by 15 minutes. Find the length of the total journey?

 A) 70 kms B) 60 kms C) 45 kms D) 30 kms

Explanation:

Let the time taken by train be 't' hrs.

Then,

40t = 35t + 35/4

t = 7/4 hrs

Therefore, Required length of the total journey d = s x t

= 40 x 7/4

= 70 kms.

3 906
Q:

Ashwin fires two bullets from the same place at an interval of 15 minutes but Rahul sitting in a bus approaching the place hears the second sound 14 minutes 30 seconds after the first. If sound travels at the speed of 330 meter per second, what is the approximate speed of bus?

 A) 330/29 m/s B) 330 x 30 m/s C) 330/14 m/s D) 330/900 m/s

Explanation:

Second gun shot take 30 sec to reach rahul imples distance between two.

given speed of sound = 330 m/s

Now, distance = 330 m/s x 30 sec

Hence, speed of the bus = d/t = 330x30/(14x60 + 30) = 330/29 m/s.

4 845
Q:

Important Time and Distance formulas with examples.

1. How to find Speed(s) if distance(d) & time(t) is given:

Ex: Find speed if a person travels 4 kms in 2 hrs?

Speed = D/T = 4/2 = 2 kmph.

2.  Similarly, we can find distance (d)  if speed (s) & time (t) is given by

Distance (D) = Speed (S) x Time (T)

Ex : Find distance if a person with a speed of 2 kmph in 2 hrs?

Distance D = S X T = 2 x 2 = 4 kms.

3.  Similarly, we can find time (t) if speed (s) &  distance (d) is given by

Time (T) =

Ex : Find in what time a person travels 4 kms with a speed of 2 kmph?

Time T = D/S = 4/2 = 2 hrs.

4. How to convert  km/hr into m/sec :

Ex : Convert 36 kmph into m/sec?

36 kmph = 36 x 5/18 = 10 m/sec

5. How to convert  m/sec into km/hr :

.

Ex : Convert 10 m/sec into km/hr?

10 m/sec = 10 x 18/5 = 36 kmph.

6.  If the ratio of the speeds of A and B is a:b, then the ratio of the times taken by them to cover the same distance is b : a.

7.  Suppose a man covers a certain distance at x km/ hr and an equal distance at y km/hr . Then, the average speed during the whole journey is $2xyx+y$ km/hr.

501
Q:

Two trains are running with speeds 30 kmph and 58 kmph respectively in the same direction. A man in the slower train passes the faster train in 18 seconds. Find the length of the faster train?

 A) 105 mts B) 115 mts C) 120 mts D) 140 mts

Explanation:

Speeds of two trains = 30 kmph and 58 kmph

=> Relative speed = 58 - 30 = 28 kmph = 28 x 5/18 m/s = 70/9 m/s

Given a man takes time to cross length of faster train = 18 sec

Now, required Length of faster train = speed x time = 70/9  x  18 = 140 mts.