a circular mirror of radius 21 cm is surrounded by a circular frame of wealth 3.5 cm find the cost of making the frame at rupees 1.50 per CM square
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16
Circumference of a circle=2xPIExRADIUS
=2x22/7x21
=132squarecm
If cost of making frame for 1cm is 1.50 means
=132X1.50
=198.00
Therefore 198 rupees needed for framing the mirror
=2x22/7x21
=132squarecm
If cost of making frame for 1cm is 1.50 means
=132X1.50
=198.00
Therefore 198 rupees needed for framing the mirror
shan15:
explain properly
original side of square is 22 cm
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Ashok Lal on is uniformly 7 meters wide and it Sinha age is 440 meters . calculate the radius of the inner circle and the area of the lawns
a circular lawn is uniformly 7 M wide and its inner address is 440 metres calculate the radius of the inner circle in the area of the lawns
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Answered by
14
let radius of mirror [r] = 21 cm
circular frame of width 3.5 cm
∴radius of mirror + frame [R] = [21 cm +3.5cm] =24.5cm
Now area of the frame= The area of the region enclosed by two concentric circles is given by:- A = π (R^2 – r^2) Here, R = 24.5cm, r = 21 cm and π = 3.14
A = π (R^2 – r^2) = π (R – r)(R + r) cm^2
[applying (a^2 – b^2) = (a – b)(a + b)] identity
A = π (24.5^2 – 21^2) = 22/7 (24.5 – 21)(24.5 + 21) cm^2
A = π (24.5^2 – 21^2) = 22/7 *3.5*45.5 cm^2
A =22*0.5*45.5 =500.5 cm^2
cost of making frame for 1cm is 1.50
⇒total cost Rs 500.5 cm^2 *1.50 =Rs 750.75
Therefore rupees needed for framing the mirror=Rs 750.75 ANS
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