Question

Unless stated otherwise use t =
7
1. The radi 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.
-ively. Find​

Answer 1

Answer with steps:

Let radii of the first and second circle be r1 and r2 respectively

r1=19 cm

r2=9 cm

Let the radius of bigger circle(the circle we need to find the radius of) be R

Circumference of circle with radius r1=c1

with radius r2=c2

Circumference of bigger circle be C

According to question,

C=c1+c2

2πR=2πr1+2πr2

2π(R)=2π(r1+r2)

Cancelling out 2π from LHS and RHS

R=r1+r2

=9+19

=28 cm

Answer 2

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radius of first circle = 19 CM

circumference of first circle = 2πr1

radius of second circle = 9cm

circumference of second circle =2πr2

now

circumference of both circle=2πr1+2πr2

= 2π(r1+r2)

=2 ×22/7 (19+9)

=2×22/7 (28)

= 2×22×4

= 176cm

Since circumference of both circle = circumference of bigger circle

2πr = 176cm

2×22/7×r = 176cm

44/7 r =176

r= 176 × 7

—

44

r= 28 cm

Hence the radius of bigger circle= 28cm.

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