Question

the radii of two circles are 4cm and 3cm .find the diameter of tge circle having area equal to the sum of the area of two circles

Answer 1

Let   R=4cm  &   r=3cm        Let the required radius be R'

Area of the circle with radius R = piR2    

                                              =pi[4]2

                                              =16pi cm2

Area of the circle with radius r = pir2

                                               =pi[3]2

                                                =9pi cm2

Therefore the area of the circlr with radius R' = area of circles with radius r + area of circle with radius R

 piR' 2 =16pi + 9pi

pi R' 2= pi [16+9]

{ pi gets cancelled }

R'2 =25        
R' = 5cm

Therefore the new radius is 5cm

Circumference=2piR'

 =2 x 22/7 x 5
 =31.42 cm   [aprox]

Aditya Sarwate answered this

its very easy

let the radii of first circle be r1=4cm

and radii of another circle be r2=3cm.

Area of first circle=2πr1

=2*π*4

=8πcm.

Area of second circle=2πr2

=2*π*3

=6πcm.

ATQ [According to given condition]

Area of first circle+Area of second circle=Area of bigger circle

=8π+6π=2πR

=14π=2πR

R=7cm.

Radius of bigger circle=7cm

Its circumfrence=2πR

=2*22/7*7

=44cm. 

Answer.

Answer 2

hope it helps.......