Ex 12.1, 1
The radii of two circles are 19 cm and 9 cm respectively. Find the radius of the circle which has circumference equal to the sum of the circumferences of the two circles.
Given that,
Radius of 1st circle = r1 = 9 cm
Radius of 2nd circle = r2 = 19 cm
Let the radius of required circle = r cm
According to question,
Circumference of required circle = Sum of circumference of two circles
Now,
Circumference of required circle = Sum of circumference of two circles
2𝜋r = 18𝜋+38𝜋
2𝜋r = 56 𝜋
r = 56𝜋/2𝜋
r = 28
Hence, radius of new circle = r = 28 cm

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Davneet Singh

Davneet Singh is a graduate from Indian Institute of Technology, Kanpur. He has been teaching from the past 12 years. He provides courses for Maths and Science at Teachoo.