Question

The radius of two circles are 9cm and 12cm.Find the radius of a circle whose area is equal to the sum of the area of these two circles​

Answer 1

Step-by-step explanation:

radius of 1st circle = r1=9cm

radius of 2nd circle = r2 = 12cm

R= radius of circle = ?

area of circle = sum of area of 1st and 2nd circles

R

$2\pi \:R = 2\pi \: r1 + 2\pi \: r2 \\ 2 \pi \: R = 2\pi \: (r1 + r2) \\ cut2\pi \: on \: both \: side \\ R = 9 + 12 \\ R = 21cm$

Answer 2

Answer :

• Radius of circle is 15cm

Given :

• The radius of two circles are 9cm and 12cm

To find :

• The radius of a circle whose area is equal to the sum of the area of these two circles

Solution :

• Radius of first circle is 9cm
• Radius of second circle is 12cm

As we know that :

• Area of circle = πr²

• Area of 1st circle = π(9)² = 81 π
• Area of 2nd circle = π(12)² = 144 π

According To Question, Given that , Area is equal to the sum of the area of these two circles then ,

⇢ πr² = (88π + 144π)

⇢ πr² = 225π

Remove π

⇢ r² = 225

⇢ r = √225

⇢ r = 15cm

Hence Radius of circle is 15cm