Question

the radii of two circle are 9 cm and 12 cm respectively find the radius of the circle whose area is equal to the sum of the areas of these two circle.

Answer 1

Answer:

15 cm

Step-by-step explanation:

Area of circle = πr².

According to the given Question,

Radius of 1st circle = 9 cm.

∴ Area of 1st circle = π(9)² = 81π

Radius of 2nd circle = 12 cm.

∴ Area of 2nd circle = π(12)² = 144π.

Now,

It is said that Area is equal to the sum of the area of these two circle.

πr² = (81π + 144π)

πr² = 225π

r² = 225

r = √225

r = 15 cm.

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Answer 2

HERE IS YOUR ANSWER -:

radius of circle 1(c1) =9cm
radius of circle 2(c2) =12cm

for finding the radius of big circle first we have to find its area So,

area of bigger circle =area of c1+area of c2

=πr^2+πr^2
=22x9x9/7+22x12x12/7

=1782/7+3168/7
= 254.5+452.5
= 707
area of bigger circle =707

radius of big circle =>

area of big circle =πr^2
707=22r^2/7

707x7=22r^2. (by cross multiply)
4949=22r^2

r^2 =4949/22
r=√225
r=15cm