# The radius of a circle whose circumference is equal to the sum of the circumferences of the two circles of diameters 36 cm and 20 cm is ______. - Mathematics

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The radius of a circle whose circumference is equal to the sum of the circumferences of the two circles of diameters 36 cm and 20 cm is ______.

• 56 cm

• 42 cm

• 28 cm

• 16 cm

#### Solution

The radius of a circle whose circumference is equal to the sum of the circumferences of the two circles of diameters 36 cm and 20 cm is 28 cm.

Explanation:

Circumference of circle = Sum of circumference of two circles

[(r_1 = 36/2 = 18  cm),(r_2 = 20/2 = 10 cm)]

⇒ 2πR = 2πr1 + 2πr2

2πR = 2π(r1 + r2)

⇒ R = r1 + r2 = 18 + 10

⇒ R = 28 cm.

Concept: Circumference of a Circle
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#### APPEARS IN

NCERT Mathematics Exemplar Class 10
Chapter 11 Area Related To Circles
Exercise 11.1 | Q 9 | Page 121

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