141. Express speed of 36 km per hr. in metres per second.

1. 1. 10 m/sec.

   
   
   

   2. 8 m/sec.

   
   
   

   3. 12 m/sec.

   
   
   

   4. 18m/sec.

   
   
   

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1. View Hint View Answer Discuss in Forum

   36 km/hr.
   

   =		36 ×	5		m/sec.
   			18

   
   = 10 m/sec.

   Correct Option: A

   36 km/hr.
   

   =		36 ×	5		m/sec.
   			18

   
   = 10 m/sec.

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142. A farmer travelled a distance of 61 km in 9 hours. He travelled partly on foot at a speed of 4 km/hour and partly on bicycle at a speed of 9 km/hour. The distance travelled on foot is :

1. 1. 14 km.

   
   
   

   2. 16 km.

   
   
   

   3. 20 km.

   
   
   

   4. 18 km.

   
   
   

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1. View Hint View Answer Discuss in Forum

   Length of journey on foot = x km. (let).
   ∴  Length of journey on cycle = (61 – x ) km.
   According to the question,
   

   Time =	Distance
   	Speed

   
   

   ∴	x	+	61 − x	= 9
   	4		9

   
   

   ⇒	9x + 244 − 4x	= 9
   	36

   
   ⇒  5x + 244 = 36 × 9 = 324
   ⇒  5x = 324 – 244 = 80
   

   ⇒  x =	80	= 16 km
   	5

   Correct Option: B

   Length of journey on foot = x km. (let).
   ∴  Length of journey on cycle = (61 – x ) km.
   According to the question,
   

   Time =	Distance
   	Speed

   
   

   ∴	x	+	61 − x	= 9
   	4		9

   
   

   ⇒	9x + 244 − 4x	= 9
   	36

   
   ⇒  5x + 244 = 36 × 9 = 324
   ⇒  5x = 324 – 244 = 80
   

   ⇒  x =	80	= 16 km
   	5

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143. A farmer travelled a distance of 61 km in 9 hours. He travelled partly on foot at a speed of 4 km/hour and partly on bicycle at a speed of 9 km/hour. The distance travelled on foot is :

1. 1. 14 km.

   
   
   

   2. 16 km.

   
   
   

   3. 20 km.

   
   
   

   4. 18 km.

   
   
   

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1. View Hint View Answer Discuss in Forum

   Length of journey on foot = x km. (let).
   ∴  Length of journey on cycle = (61 – x ) km.
   According to the question,
   

   Time =	Distance
   	Speed

   
   

   ∴	x	+	61 − x	= 9
   	4		9

   
   

   ⇒	9x + 244 − 4x	= 9
   	36

   
   ⇒  5x + 244 = 36 × 9 = 324
   ⇒  5x = 324 – 244 = 80
   

   ⇒  x =	80	= 16 km
   	5

   Correct Option: B

   Length of journey on foot = x km. (let).
   ∴  Length of journey on cycle = (61 – x ) km.
   According to the question,
   

   Time =	Distance
   	Speed

   
   

   ∴	x	+	61 − x	= 9
   	4		9

   
   

   ⇒	9x + 244 − 4x	= 9
   	36

   
   ⇒  5x + 244 = 36 × 9 = 324
   ⇒  5x = 324 – 244 = 80
   

   ⇒  x =	80	= 16 km
   	5

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144. A man travelled a distance of 61 km. in 9 hours, partly by walking at the speed of 4 km./hr. and partly on bicycle at the speed of 9 km./hr. The distance covered by walking is

1. 1. 16 km.

   
   
   

   2. 12 km.

   
   
   

   3. 15 km.

   
   
   

   4. 17 km.

   
   
   

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1. View Hint View Answer Discuss in Forum

   Let the distance covered on foot be x km.
   ∴  Distance covered on cycle = (61 – x) km.
   

   Time =	Distance
   	Speed

   
   

   ∴	x	+	61 − x	= 9
   	4		9

   
   

   ⇒	x	−	x	= 9 −	61
   	4		9		9

   
   

   ⇒	9x − 4x	=	81 − 61
   	36		9

   
   

   ⇒	5x	=	20
   	36		9

   
   

   ⇒   x =	20	×	36	= 16 km.
   	9		5

   Correct Option: A

   Let the distance covered on foot be x km.
   ∴  Distance covered on cycle = (61 – x) km.
   

   Time =	Distance
   	Speed

   
   

   ∴	x	+	61 − x	= 9
   	4		9

   
   

   ⇒	x	−	x	= 9 −	61
   	4		9		9

   
   

   ⇒	9x − 4x	=	81 − 61
   	36		9

   
   

   ⇒	5x	=	20
   	36		9

   
   

   ⇒   x =	20	×	36	= 16 km.
   	9		5

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145. Sound travels 330 metre in a second.When the sound follows the flash of lightning after 10 seconds the thunder cloud will be at a distance of :

1. 1. 1300 metre

   
   
   

   2. 2000 metre

   
   
   

   3. 3650 metre

   
   
   

   4. 3300 metre

   
   
   

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1. View Hint View Answer Discuss in Forum

   Distance = Speed × Time
   = 330 × 10 = 3300 metre

   Correct Option: D

   Distance = Speed × Time
   = 330 × 10 = 3300 metre

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