Question

The ratio of diameters of two circle is 5:6.find the ratio of their circumference.

Answer 1

Let the diameter of the two circles be d1 and d2.

d1 : d2 = 5x : 6x

The radius of the first circle = 5x/ 2 = 2.5x

The radius of the second circle = 6x /3 = 3x

Circumference of the first circle = 2πr

= 2 × 22/7 × 2.5x

= 110x /7

Circumference of the second circle = 2πr

= 2× 22/7 × 3x

= 132x /7

Ratio of the circumference of the two circles = 110x/7 : 132x/7

( x and 7 are common. Common values are cancelled).

Therefore, Ratio of the circumference of the two circles = 110:132

= 5:6

Ans. = The ratio is 5:6.



Hope it helps!!!

Answer 2

Heya User,

--> Let the circles have diameters, ummm, '2a' and '2b' 
--> Their circumferences --> 2πa , 2πb

--> Given, the ratio of diameters = 5 : 6
--> However, this is ---> 2a : 2b = 5 : 6
--> A common ratio to both expressions: π  ---> 2πa : 2πb = 5 : 6 

-->This implies that Ratio of Circumference of both circles = 5 : 6
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Anyways, for such a question :->
--> Ratio [ Circumference ] = Ratio [ Radius ] = Ratio [ Diameter ]
--> Ratio [ Area ] = { Ratio [ Radius ] }²   

--> The above holds for all circles .. ☺xD