311. If a boy takes as much time in running 10 m as a car takes in covering 25 m, the distance covered by the boy during the time the car covers 1 km, is ?

1. 1. 400 m.

   
   
   

   2. 40 m.

   
   
   

   3. 250 m.

   
   
   

   4. 650 m.

   
   
   

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1. View Hint View Answer Discuss in Forum

   Let distance covered by boy is Y.
   Then, 25 : 10 : : 1000 : Y
   
   

   Correct Option: A

   Let distance covered by boy is Y.
   Then, 25 : 10 : : 1000 : Y
   ⇒ Y = (10 x 1000)/25 = 400 m

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312. A man goes uphill with an average speed of 35 km/hr, and covers down with an average speed of 45 km/hr. The distance travelled in both the cases being the same , the average speed for the entire journey is ?

1. 1. 38 ³/₈ km/hr.

   
   
   

   2. 39 ³/₈ km/hr.

   
   
   

   3. 40 km/hr

   
   
   

   4. None of these

   
   
   

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1. View Hint View Answer Discuss in Forum

   Average speed = 2uv / (u + v)
   
   

   Correct Option: B

   Average speed = 2uv / (u + v)
   = ( 2 x 35 x 45) / (35 + 45) km/hr.
   = 39 ³/₈ km/hr

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313. Suresh started cycling along the boundaries of a square field from corner point A. After half an hour, he reached the corner point C, diagonally opposite to A, if his speed was 8km/hr , what is the area of the field in square km.?

1. 1. 64

   
   
   

   2. 8

   
   
   

   3. 4

   
   
   

   4. Cannot be determined

   
   
   

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1. View Hint View Answer Discuss in Forum

   Length of two sides of square
   = 8 x 1/2 km.
   = 4 km.

   Correct Option: C

   Length of two sides of square
   = 8 x 1/2 km.
   = 4 km.
   
   ∴ Area of the field = 2 x 2 sq. km
   = 4 sq. km.

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314. A man travels for 5 hours 15 minutes. If he covers the first half of the journey at 60 km/h and rest at 45 km/h. Find the total distance travelled by him.

1. 1. 1028	6	km.
      	7

   
   
   

   2. 189 km.

   
   
   

   3. 378 km.

   
   
   

   4. 270 km.

   
   
   

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1. View Hint View Answer Discuss in Forum

   Let the distance covered be 2x km.
   

   Time =	Distance
   	Speed

   
   According to the question,
   

   x	+	x	= 5	15	=	1
   60		45		60		4

   
   

   ⇒	3x + 4x	=	21
   	180		4

   
   

   ⇒ 7x =	21	× 180
   	4

   
   

   ⇒  x =	21 × 180	= 135 km.
   	4 × 7

   
   ∴  Length of total journey
   = 2 × 135 = 270 km.

   Correct Option: D

   Let the distance covered be 2x km.
   

   Time =	Distance
   	Speed

   
   According to the question,
   

   x	+	x	= 5	15	=	1
   60		45		60		4

   
   

   ⇒	3x + 4x	=	21
   	180		4

   
   

   ⇒ 7x =	21	× 180
   	4

   
   

   ⇒  x =	21 × 180	= 135 km.
   	4 × 7

   
   ∴  Length of total journey
   = 2 × 135 = 270 km.

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315. Sriya with her family travelled from Bolpur to Suri by car at a speed of 40 km/hr and returned to Bolpur at a speed of 50 km/hr. The average speed for the whole journey is

1. 1. 44	4	km/hr
      	9

   
   
   

   2. 45 km/hr

   
   
   

   3. 45	1	km/hr
      	2

   
   
   

   4. 44.78 km/hr

   
   
   

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1. View Hint View Answer Discuss in Forum

   Average speed of journey =		2xy		kmph
   		x + y

   
   

   ⇒	2 × 40 × 50	=	2 × 40 × 50
   	40 + 50		90

   
   

   ⇒	400	= 44	4	kmph
   	9		9

   Correct Option: A

   Average speed of journey =		2xy		kmph
   		x + y

   
   

   ⇒	2 × 40 × 50	=	2 × 40 × 50
   	40 + 50		90

   
   

   ⇒	400	= 44	4	kmph
   	9		9

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