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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 36cm and 20 cm is (A) 56 cm (B) 42 cm (C) 28 cm (D) 16 cm

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

(A) 56 cm                   (B) 42 cm                    (C) 28 cm                    (D) 16 cm

Answers (1)

(C) 28 cm

Solution

Circumference of circle = 2 \pi r

Diameter of first circle (d1) = 36

Radius (r1) =\frac{d_{1}}{2}=\frac{36}{2}=18

Diameter of second circle (d2) = 20 cm

Radius (r2)=\frac{d_{2}}{2}=\frac{20}{2}=10

Let Radius of 3rd circle = R cm

According to question

\\2 \pi (18)+2 \pi (10)=2 \pi R\\ 2 \pi (18+10)=2 \pi R \\ R=28 cm

Posted by

infoexpert24

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