Question

The inner diameter of a circular well is 3.5 m. It is 10 m deep Find:
(i) inner curved surface area.
(ii) the cost of plastering this curved surface at the rate of Rs. 40 per m².

Answer 1

The inner curved surface area is 110 square meter

The cost of plastering this curved surface at the rate of Rs. 40 per square meter is Rs 4400

Solution:

Given that,

Inner diameter of circular well = 3.5 meter

Therefore,

$Inner\ radius = \frac{3.5}{2} = 1.75$

Depth of well = h = 10 meter

Find the inner curved surface area

$\text{ Inner curved surface area } = 2 \pi r h\\\\\text{ Inner curved surface area } = 2 \times \frac{22}{7} \times 1.75 \times 10\\\\\text{ Inner curved surface area } = 110\ m^2$

Find the cost of plastering this curved surface at the rate of Rs. 40 per square meter

$1\ m^2 = Rs. 40$

Therefore,

$110\ m^2 = 40 \times 110 = 4400$

Thus the cost of plastering this curved surface at the rate of Rs. 40 per square meter is Rs 4400

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Answer 2

Step-by-step explanation:

Given,

The inner diameter of a circular well (d) = 3.5 m

∴ The inner radius of a circular well (r) = $\dfrac{3.5}{2}$ m = 1.75 m

The deep of a circular well (h) = 10 m

i)  inner curved surface area

The inner curved surface area (cylinder) = 2πrh

= $2\times \dfrac{22}{7} \times 1.75\times 10m^{2}$

= 44 × 25 m^{2}

= 1100 m^{2}

∴ The inner curved surface area (cylinder) = 1100 m^{2}