<PRE><B>Question 238034</B>
sol:
in this problem 3 circles are given
let the radius of the 1 st circle be r
circumference of 1st circle=2*pi*r
and diameter of the 2nd circle=36cm
circumference of 2nd circle=pi*diameter of 2nd circle=pi*36=36pi
diameter of the 3rd circle=20cm
circumference of the 3rd circle=pi*20=20pi
according to the problem
circumference of 1st circle=circumference of 2nd circle +circumference of 3rd circle
2*pi*r=36pi+20pi
2*pi*r=56pi
dividing both sides by pi
2*pi*r/pi=56pi/pi
2r=56
dividing both sides by 2
2r/2=56/2
r=28cm

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