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 cm?​

Answer 1

Answer:

The width of the frame around the photo is 2 cm and the cost of painting it with a metallic colour is Rs.167.1999

Step-by-step explanation:

Outer radius of circular plate R = 20 cm

Inner radius of circular plate r = 18 cm

Width = Outer radius - Inner radius = 20-18 = 2 cm

Area of frame = Outer area - inner area

Area of frame =\pi R^2 - \pi r^2πR

2

−πr

2

Area of frame =\frac{22}{7}(20^2-18^2)=238.857 cm^2

7

22

(20

2

−18

2

)=238.857cm

2

Cost of painting 1 sq.cm. = rs.0.7

Cost of painting 238.857 sq.cm. =0.7 \times 238.857 = Rs.167.19990.7×238.857=Rs.167.1999

Hence the width of the frame around the photo is 2 cm and the cost of painting it with a metallic colour is Rs.167.1999

#Learn more:

A mirror of length 20cm and width 15cm is to be framed with a 2 cm wide frame . find the area of the frame required . Also find the cost of framing at the rate of 15 per cm2