721. The wheel of a motor car makes 1000 revolutions in moving 440 m. The diameter (in metre) of the wheel is
     

1. 1. 0.44
      

   
   
   

   2. 0.14
      

   
   
   

   3. 0.24
      

   
   
   

   4. 0.34

   
   
   

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1. View Hint View Answer Discuss in Forum

   Using Rule 7,
   Distance covered by wheel in one revolution
   = Circumference of wheel
   

   = π × diameter =	440
   	1000

   
   

   ⇒	22	× diameter =	440
   	7		1000

   
   

   ⇒ Diameter =	440	×	7
   	1000		22

   
   = 0.14 m

   Correct Option: B

   Using Rule 7,
   Distance covered by wheel in one revolution
   = Circumference of wheel
   

   = π × diameter =	440
   	1000

   
   

   ⇒	22	× diameter =	440
   	7		1000

   
   

   ⇒ Diameter =	440	×	7
   	1000		22

   
   = 0.14 m

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722. A bicycle wheel makes 5000 revolutions in moving 11km.Then the radius of the wheel (in cm) is (Take π = 22/7 )
     

1. 1. 70
      

   
   
   

   2. 35
      

   
   
   

   3. 17.5
      

   
   
   

   4. 140

   
   
   

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1. View Hint View Answer Discuss in Forum

   Using Rule 7,
   Distance covered by wheel in one revolution =
   

   Circumference of wheel =	11000	=	11	metre
   	5000		5

   
   

   =	11	× 100 cm = 220 cm
   	5

   
   ∴ 2πr = 220
   

   ⇒ 2 ×	22	× r = 220 cm
   	7

   
   

   ⇒ r =	220 × 7	= 35 cm
   	2 × 22

   Correct Option: B

   Using Rule 7,
   Distance covered by wheel in one revolution =
   

   Circumference of wheel =	11000	=	11	metre
   	5000		5

   
   

   =	11	× 100 cm = 220 cm
   	5

   
   ∴ 2πr = 220
   

   ⇒ 2 ×	22	× r = 220 cm
   	7

   
   

   ⇒ r =	220 × 7	= 35 cm
   	2 × 22

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723. Three circles of diameter 10 cm each, are bound together by a rubber band, as shown in the figure.
     
     The length of the rubber band, (in cm) if it is stretched as shown, is
     

1. 1. 30
      

   
   
   

   2. 30 + 10π
      

   
   
   

   3. 10π
      

   
   
   

   4. 60 + 20π

   
   
   

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1. View Hint View Answer Discuss in Forum

   Length of the rubber band = 3d + 2πr
   = (30 + 10π) cm
   

   Correct Option: B

   Length of the rubber band = 3d + 2πr
   = (30 + 10π) cm
   

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724. If a chord of length 16 cm is at a distance of 15 cm from the centre of the circle, then the length of the chord of the same circle which is at a distance of 8 cm from the centre is equal to
     

1. 1. 10 cm
      

   
   
   

   2. 20 cm
      

   
   
   

   3. 30 cm
      

   
   
   

   4. 40 cm

   
   
   

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1. View Hint View Answer Discuss in Forum

   The chord nearer to the centre is larger.
   

   ∴	15	=	x
   	8		16

   
   

   ⇒ x =	15 × 16	= 30 cm
   	8

   Correct Option: C

   The chord nearer to the centre is larger.
   

   ∴	15	=	x
   	8		16

   
   

   ⇒ x =	15 × 16	= 30 cm
   	8

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725. A semicircular shaped window has diameter of 63 cm. Its perimeter equals (π = 22/7)
     

1. 1. 126 cm
      

   
   
   

   2. 162 cm
      

   
   
   

   3. 198 cm
      

   
   
   

   4. 251 cm

   
   
   

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1. View Hint View Answer Discuss in Forum

   Using Rule 14,
   Perimeter of semi-circular shaped window
   = (πr + 2r) cm = r (π + 2) cm
   

   =	63		22	+ 2		cm
   	2		7

   
   

   =	63	×	36	= 162cm
   	2		7

   Correct Option: B

   Using Rule 14,
   Perimeter of semi-circular shaped window
   = (πr + 2r) cm = r (π + 2) cm
   

   =	63		22	+ 2		cm
   	2		7

   
   

   =	63	×	36	= 162cm
   	2		7

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