Question

Find the area of a circular ring formed by the circumference of two concentric circles of radii 11 m and 4 m . Also , find the cost of painting this ring at the rate of Rupees 21 per meter square .

$area \: of \: a \: cirle \: = \pi \: r \: square$
ANSWER STEP BY STEP ​

Answer 1

Step-by-step explanation:

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Answer 2

Here≈

Area of ring= outer surface area - inner surface area.

Given ≈

• outer radius =11 m
• Inner radius = 4 m
• Rate = ₹21/m^2

Taken≈

• Area of circle =πr^2
• Area of ring = (πR^2 - πr^2)

So that ≈

» π(R^2-r^2)

» 22/7(11×11-2×11×4+4×4)

» 22/7(121+16-88)

» 22/7(137-88)

» 22/7(49)

»154 m^2

Cost of painting it≈

• Total area to be painted × cost of painting

» 154×21=3234

Hence the total cost of painting the ring will be ₹3234.

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