two circular metallic discs have a thickness of 15mm. Their areas are in the ratio of 9:1. The smaller dia disc is pressed against the bigger disc and rotated around it on a flat surface. How many times will the small disc rotate before it completes one cycle of the bigger disc:

• Ratio of area is 9:1
  so ratio of radius is 3:1
  so ratio of perimeter is also 3:1...
  hence ,Answer is 3
• 11 years agoHelpfull: Yes(2) No(0)
• let r1 be the radius of larger disk r2 be the radius of small disk
  
  pi (r1)² /pi(r2)² =9/1
  
  r1/r2 =3/1
  
  let r1 =3x and r2 = x
  
  2 *pi*r1 = 6pix
  2*pi *r2 =2pix
  
  perimeter are in the ratio 3:1
  
  therefore small disc rotate 3 times in one rotation of larger disc
  
• 11 years agoHelpfull: Yes(1) No(0)