Question

The inner diameter of a circular well is 3.5m. It is 10m deep. Find

(i) its inner curved surface area,

(ii) the cost of plastering this curved surface at the rate of Rs. 40 per m^2.

(Assume π = 22/7)​

Answer 1

Given :

† The inner diameter of a circular well is 3.5m.

† It is 10m deep.

To find :

(i) its inner curved surface area,

(ii) the cost of plastering this curved surface at the rate of Rs. 40 per m².

Solution :

As we know that,

$\boxed{ \pink{\sf \: Diameter \: of \: circle \: = 2 \times Radius}}$

$\sf \: \implies \: 3.5 \: = 2 \times Radius$

$\sf \: \implies \: \dfrac{3.5}{2} = Radius$

$\sf \: \implies \: 1.75 \: meter = Radius$

Now,

$\sf : \implies \: \: Height = 10 \: meter$

$\sf : \implies \: \: Radius = 1.75 \: meter$

So,

$\boxed{ \pink{\sf \: Curved \: surface \: area \: of \: circular \: well = 2\pi \times r \times h}}$

$\sf \implies \: 2 \times \dfrac{22}{7} \times 1.75 \times 10$

$\sf \implies \: \dfrac{44}{17} \times 17.5$

$\sf \implies \: \dfrac{770}{7} \: m ^{2}$

$\sf \implies \: 110 \: m ^{2}$

★curved surface area of the circular well = 110 m²

Hence,

★ the cost of plastering this curved surface at the rate of Rs. 40 per m^2. = 110 × 40 = RS. 4400