8 cm6cm 8cm0Fig. 12.5Fig. 12.6Fig. 12:6 shows two concentric circles withcentre O and radius 7 and R respectively.If R =3r, express the area of the shadedpart in terms of 77 and r.

In this case, we'll have to carry out several steps to find the solution.
Step 01:
Data:
ring:
R = 3r
Step 02:
geometry:
shaded area:
we must analyze the figure to find the solution.
A = πR² - πr²
A = π(3r)² - πr² = π (9r² - r²) = π (8r²)
The answer is:
A = π (8r²)