Question

A circular photo frame has an outer radius
20 cm and inner radius 18 cm. Find the
width of the frame around the photo.
Also find the cost of painting it with a
metallic colour at the rate of 0.7 per cm2.​

Answer 1

$\huge{\bold{\underline{\underline{Question:-}}}}$

A circular photo frame has an outer radius

20 cm and inner radius 18 cm. Find the

width of the frame around the photo.

Also find the cost of painting it with a

metallic colour at the rate of 0.7 per cm2.

$\huge{\bold{\underline{\underline{Solution:-}}}}$

Outer radius = 20cm

Inner radius = 18cm

Width of frame = 20cm-18cm = 2cm

Area of width of frame

= π[(R)²-(r²)]

$= \frac{22}{7} (400 - 324)$

$= \frac{22}{7} \times 76$

$= \frac{1672}{7}$

$= {238.85 \: cm}^{2}$

Now,

Cost of painting 1cm² = Rs. 0.7

Cost of painting 238.85cm² = 238.85 * 0.7

= Rs. 167.195