Question

A circular well radius 3m if a platform of uniform width of 1.5m is laid around it find the area of the platform

Answer 1

Let the radius of the well be r

and the radius of well and platform be R

then

area of well

$\pi {r}^{2}$

$\pi \times 3 \times 3$

$= 28.26 \: cm {}^{2}$

area of well with platform

$\pi \times 4.5 \times 4.5$

$= 63.585 \: {cm}^{2}$

area of platform

$63.585 - 28.26$

$= 35.325 \: {cm}^{2}$

Answer 2

Step-by-step explanation:

Given that,

the radius of circular well = 3 cm

So, Area of circular well = 22/7 * r^2

Taking 22/7 = 3.14,

= 3.14* 9 cm^2

=28.26 cm^2

Since, Width of platform laid around well is 1.5 m.

so, the outer radius

= (3+1.5)cm=4.5cm

Then, the Area of outer boundary

= 22/7 * r^2

Taking 22/7 = 3.14,

= 3.14 * (4.5cm)^2

= 3.14 * 20.25 cm^2

= 63.585 cm^2

Now,

Since, Area of outer boundary of circular well is 63.585 cm^2 .

so, the area of platform

= Area of outer boundary of circular well - Area of circular well

= (63.585 - 28.26)cm^2

= 35.325 cm^2