self Maths Puzzle Logical Reasoning Mathematical Reasoning

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:

Read Solution (Total 2)

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
12 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
12 years agoHelpfull: Yes(1) No(0)

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