Question

The radii of two concentric circles are 4cm and 5cm . The difference in the areas of these two circles is a) π b) 7π c) 9π d) 13π​

Answer 1

Answer:

$9\pi$

Step-by-step explanation:

Given data,

The radii of two concentric circles are $4cm$ and $5cm$.

We know that the area of a circle = $\pi r^{2}$

Area of the circle with radius  = $\pi \times4\times4=16\pi$

Area of the circle with radius  = $\pi \times5\times5=25\pi$

The difference in the areas of these two circles $=25\pi-16\pi =9\pi$

Therefore, the answer is $9\pi$.

Answer 2

Given,

The radii of $2$ concentric circles is $4cm$ and $5cm$.

Formula,

Area of circle is $\pi r^{2}$

$A=\pi r^{2}$

Area of first circle $(r=4cm)$

$A=\pi\times4\times4$

$A=16\pi$

Area of second circle$(r=5cm)$

$A=\pi \times5\times5$

$A=25\pi$

Difference between area of two circles $=25\pi -16\pi =9\pi$

Therefore, the difference between area of two circles is $9\pi$.