401. A person travels 600 km by train at 80km/hr, 800 km by ship at 40 km/hr 500 km by aeroplane at 400 km/hr and 100 km by car at 50km/hr. What is the average speed for the entire distance ?

1. 1. 65	5	km./hr.
      	123

   
   
   

   2. 60 km./hr.

   
   
   

   3. 60	5	km./hr.
      	123

   
   
   

   4. 62 km./hr.

   
   
   

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1. View Hint View Answer Discuss in Forum

   Total time =	600	+	800	+	500	+	100
   	80		40		400		50

   
   

   =	246	hours.
   	8

   
   

   Average speed =	600 + 800 + 500 +100
   	246
   	8

   
   

   =	2000 × 8
   	246

   
   

   = 65	5	km/hr.
   	123

   Correct Option: A

   Total time =	600	+	800	+	500	+	100
   	80		40		400		50

   
   

   =	246	hours.
   	8

   
   

   Average speed =	600 + 800 + 500 +100
   	246
   	8

   
   

   =	2000 × 8
   	246

   
   

   = 65	5	km/hr.
   	123

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402. A train moves with a speed of 30 kmph for 12 minutes and for next 8 minutes at a speed of 45 kmph. Find the average speed of the train:

1. 1. 37.5 kmph

   
   
   

   2. 36 kmph

   
   
   

   3. 48 kmph

   
   
   

   4. 30 kmph

   
   
   

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1. View Hint View Answer Discuss in Forum

   Average speed =	Total distance
   	time taken

   
   

   =	30 ×	12	+ 45 ×	8
   		60		60
   	12	+	8
   	60		60

   
   = 12 × 3 = 36 kmph

   Correct Option: B

   Average speed =	Total distance
   	time taken

   
   

   =	30 ×	12	+ 45 ×	8
   		60		60
   	12	+	8
   	60		60

   
   = 12 × 3 = 36 kmph

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403. A man covers half of his journey at 6km/hr and the remaining half at 3km/hr. His average speed is

1. 1. 9 km/hr

   
   
   

   2. 4.5 km/hr

   
   
   

   3. 4 km/hr

   
   
   

   4. 3 km/hr

   
   
   

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1. View Hint View Answer Discuss in Forum

   If the same distance are covered at different speed of x kmph and y kmph, the average speed of the
   

   whole journey is given by =	2xy	kmph.
   	x + y

   
   

   ∴  Required average speed =	2 × 6 × 3	=	36	= 4 kmph
   	6 + 3		9

   Correct Option: C

   If the same distance are covered at different speed of x kmph and y kmph, the average speed of the
   

   whole journey is given by =	2xy	kmph.
   	x + y

   
   

   ∴  Required average speed =	2 × 6 × 3	=	36	= 4 kmph
   	6 + 3		9

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404. A man goes from A to B at a uniform speed of 12 kmph and returns with a uniform speed of 4 kmph His average speed (in kmph) for the whole journey is :

1. 1. 8

   
   
   

   2. 7.5

   
   
   

   3. 6

   
   
   

   4. 4.5

   
   
   

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1. View Hint View Answer Discuss in Forum

   If two equal distances are covered at two unequal speed of x kmph and y kmph, then average
   

   speed =		2xy		kmph
   		x + y

   
   

   =	2 × 12 × 4	=	96	= 6 kmph
   	12 + 4		16

   Correct Option: C

   If two equal distances are covered at two unequal speed of x kmph and y kmph, then average
   

   speed =		2xy		kmph
   		x + y

   
   

   =	2 × 12 × 4	=	96	= 6 kmph
   	12 + 4		16

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405. A train covers a distance of 3584 km in 2 days 8 hours. If it covers 1440 km on the first day and 1608 km on the second day, by how much does the average speed of the train for the remaining part of the journey differ from that for the entire journey ?

1. 1. 3 km/hour more

   
   
   

   2. 3 km/hour less

   
   
   

   3. 4 km/hour more

   
   
   

   4. 5 km/hour less

   
   
   

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1. View Hint View Answer Discuss in Forum

   Remaining distance
   = (3584 – 1440 – 1608) km
   = 536 km.
   

   This distance is covered at the rate of	536	= 67 kmph.
   	8

   
   Average speed of whole journey
   

   =	3584	= 64 kmph
   	56

   
   ∴  Required difference in speed
   = (67 – 64) kmph i.e. = 3 kmph
   more

   Correct Option: A

   Remaining distance
   = (3584 – 1440 – 1608) km
   = 536 km.
   

   This distance is covered at the rate of	536	= 67 kmph.
   	8

   
   Average speed of whole journey
   

   =	3584	= 64 kmph
   	56

   
   ∴  Required difference in speed
   = (67 – 64) kmph i.e. = 3 kmph
   more

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