Question

The inner diameter of a circular well is 3.5 m. It is
10 m deep. Find the cost of plastering its inner curved
surface at ₹4 per square metre.​

Answer 1

See the image for diagram...

Finding curved surface area of cylinder----2πrh

radius=3.5/2

CSA=

$2 \times \frac{22}{7} \times \frac{3.5}{2} \times 10$

110 m sq.

cost of plastering = 110 × 4 = 440 ₹

we just have to find out the CURVED SURFACE AREA by putting it in the formula and then we have to multiply the CSA by 4 to get the cost of plastering. To find the radius we just have to divide the diameter by 2.

#BAL

#answerwithquality

Answer 2

Appropriate Question :-

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• $\textsf{The Inner Radius of a Circular Well is 3.5 m. It is 10 m Deep. Find The Cost of Plastering the Inner Curved Surface at the Rate of Rs. 20/ m²}$

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Required Solution :-

⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀

• $\textsf{Inner Radius (r) = 3.5 m and Height/ Depth (h) = 10 m}$

⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀

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$\begin {aligned} \red {\bold {☯ \;Inner\: Curved\: Surface\: Area\: of\: the\: Well}} & = \blue {\bold {(2 \pi rh)\: sq.\: units}} \\\\& \Rightarrow 2 \times \frac{22}{7} \times 3.5 \times 10\\\\& \Rightarrow \frac{44}{7} \times 35 = \red {\bold {220\: m^2\;☯}} \end {aligned}$

⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀

$\textsf{The Inner Curved Surface Area of the Well = 220 m²}$

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$\begin {aligned} \green{\bold {⚛ \;Cost\: of\: Painting\: the\: Inner\: Curved\: Surface\: Area\: of\: the\: Well}} & = Rs. (20 \times 220)\\\\& = \red{\bold {Rs.\: 4,40\; ⚛}}\end {aligned}$

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Hence,

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• $\textsf{The Cost of Painting the Inner Curved Surface Area of the Well is Rs. 4,40 }$

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