Question

The inner diameter of a circular well is 3.5 m. It is 10 m deep. Find: (i) its inner curved surface area. (ii) the cost of plastering this curved surface at the rate of 40 per W.

Answer 1

Answer:

• Given

Inner diameter of a circular well = 3.5 m

Depth of a circular wall = 10 m

• To find

Its inner curved surface area

Cost of this curved surface at the rate of 40 per m².

• Solution

• Inner curved surface area = 2πrh

where,

r = radius of the well

h = height of the well

Take π = 22/7

• Diameter = 3.5 m

⇒ Radius = Diameter/2

⇒ 3.5/2

⇒ 1.75 m

Substitute the given values,

⇒ 2 × 22/7 × 1.75 × 10

⇒ 110 m²

• Inner curved surface area = 110 m²

(ii) Cost of this curved surface at the rate of 40 per m².

⇒ 110 × 40

⇒ Rs. 4400

• Cost of this curved surface at the rate of 40 per m² = Rs. 4400 ⠀⠀⠀⠀⠀⠀⠀⠀⠀

Answer 2

Given:-

• Inner diameter of well =3.5m

• Inner radius of well (r) = 3.5/2m

• Height of well (h)=10m

step-by-step explaination:-

(i) Therefore,

Inner curved surface area of well = 2πrh

• => 2× 22/7 × 3.5/2 × 10

• => 110m²

Now,

Cost of plastering = Rs.40 per m²

Therefore,

(ii) Cost of plastering this well = 40 × 110 = Rs.4400

_________________________________________