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Q:

# P, Q and R start simultaneously from A to B. P reaches B, turns back and meet Q at a distance of 11 km from B. Q reached B, turns back and meet R at a distance of 9 km from B. If the ratio of the speeds of P and R is 3:2, what is the distance between A and B ?

 A) 99 B) 100 C) 89 D) 1

Answer:   A) 99

Explanation:

Let, Distance between A and B = d

Distance travelled by P while it meets Q = d + 11

Distance travelled by Q while it meets P = d – 11

Distance travelled by Q while it meets R = d + 9

Distance travelled by R while it meets Q = d – 9

Here the ratio of speeds of P & Q => SP : SQ = d + 11 : d – 11

The ratio of speeds of Q & R => SQ : SR = d + 9 : d – 9

But given Ratio of speeds of P & R => P : R = 3 : 2

=> $\frac{\left(d+11\right)\left(d+9\right)}{\left(d-11\right)\left(d-9\right)}$ = 3/2

=>  d = 1, 99

=> d = 99 satisfies.

Therefore, Distance between A and B = 99

Q:

Important Time and Distance formulas with examples.

Answer

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 $\frac{\mathbf{2}\mathbf{xy}}{\mathbf{x}\mathbf{+}\mathbf{y}}$ km/hr.

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80
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

Answer & Explanation Answer: 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.

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0 79
Q:

A train-A passes a stationary train B and a pole in 24 sec and 9 sec respectively. If the speed of train A is 48 kmph, what is the length of train B?

 A) 200 mts B) 180 mts C) 160 mts D) 145 mts

Answer & Explanation Answer: A) 200 mts

Explanation:

Length of train A = 48 x 9 x 5/18 = 120 mts

Length of train B = 48 x 24 x 5/18 - 120

=> 320 - 120 = 200 mts.

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1 233
Q:

Tilak rides on a cycle to a place at speed of 22 kmph and comes back at a speed of 20 kmph. If the time taken by him in the second case is 36 min. more than that of the first case, what is the total distance travelled by him (in km)?

 A) 132 km B) 264 km C) 134 km D) 236 km

Answer & Explanation Answer: B) 264 km

Explanation:

Let the distance travelled by Tilak in first case or second case = d kms

Now, from the given data,

d/20 = d/22 + 36 min

=> d/20 = d/22 + 3/5 hrs

=> d = 132 km.

Hence, the total distance travelled by him = d + d = 132 + 132 = 264 kms.

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0 177
Q:

A train covers 180 km distance in 5 hours. Another train covers the same distance in 1 hour less. What is the difference in the distances covered by these trains in one hour if they are moving in the same direction?

 A) 15 kms B) 9 kms C) 6 kms D) 18 kms

Answer & Explanation Answer: B) 9 kms

Explanation:

The first train covers 180 kms in 5 hrs

=> Speed = 180/5 = 36 kmph

Now the second train covers the same distance in 1 hour less than the first train => 4 hrs

=> Speed of the second train = 180/4 = 45 kmph

Now, required difference in distance in 1 hour = 45 - 36 = 9 kms.

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4 354
Q:

Chennai express left Hyderabad for Chennai at 14 : 30 hours, travelling at a speed of 60 kmph and Charminar Express left Hyderabad for Chennai on the same day at 16 : 30 hours, travelling at a speed of 80 kmph. How far away from Hyderabad will the two trains meet?

 A) 360 kms B) 480 kms C) 520 kms D) 240 kms

Answer & Explanation Answer: B) 480 kms

Explanation:

Now, the distance covered by Chennai express in 2 hrs = 60 x 2 = 120 kms

Let the Charminar Express takes 't' hrs to catch Chennai express

=> 80 x t = 60 x (2 + t)

=> 80 t = 120 + 60t

=> t = 6 hrs

Therefore, the distance away from Hyderabad the two trains meet = 80 x 6 = 480 kms.

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6 295
Q:

A man covers half of his journey by train at 60 km/hr, half of the remaining by bus at 30 km/hr and the rest by cycle at 10 km/hr. Find his average speed during the entire journey?

 A) 32 kmph B) 20 kmph C) 18 kmph D) 24 kmph

Answer & Explanation Answer: D) 24 kmph

Explanation:

Let the total distance of the journey of a man = d kms

Now, the average speed of the entire journey =  = 24 kmph.

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7 591
Q:

The respective ratio between the speed of a bike, a van  and lorry is 3 : 5 : 2. The speed of the van is 250 percent of the speed of the lorry which covers 360 km in 12 hours. What is the average speed of the bike and the van together?

 A) 60 kmph B) 62 kmph C) 64 kmph D) 63 kmph

Answer & Explanation Answer: A) 60 kmph

Explanation:

Speed of lorry = $\frac{\mathbf{360}}{\mathbf{12}}$ = 30 kmph

Speed of van = = 75 kmph

Speed of bike = = 45 kmph

Therefore, now required average speed of bike and van  = = 60 kmph.

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6 406