Question

the radii of two circles are 25cm and 18cm find the radius of the circle which has circumference equal to the sum of circumference of these two circles

Answer 1

hello frnd!!

here's ur answer...

circumference of circle(radius=25cm)=2πr

=2×22/7×25

=44/7×25

=1100/7cm

circumference of circle(radius=18cm)=2πr

=2×22/7×18

=44/7×18

=792/7cm

sum of their circumference=1100+792/7

=1892/7cm

circumference of the circle=1892/7

2πr=1892/7

2×22/7×r=1892/7

44/7×r=1892/7

r=1892/7×7/44

r=43cm

therefore radius of the circle whose circumference is the sum of circumference of the two circle is 43cm.

hope this helps...

Answer 2

r1=25 cm
r2=18 cm
C1=2πr1 and C2=2πr2 , where c is circumference.

Let, the radius of required circle be r and its circumference be 2πr

According to the question, we get

2πr=2πr1+2πr2
2πr=2π(r1+r2)
r=r1+r2

Since r1=25 and r2=18

So, we get the radius of the required circle is

r=(25+18) cm =43 cm ans