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ayush19
given that curved portion is 3/4 i.e 3/4*360 ; 270*
so the part which is not curved would be 360-270 = 90*
Hope this helps.

ayush19
Dillesh4096
Bunuel

The figure shows the shape of tunnel entrance. If the curved portion is 3/4 of a circle and the base of the entrance is 12 feet across, what is the perimeter, in feet, of the curved portion of the entrance?

A. \(9\pi\)

B. \(12\pi\)

C. \(9\pi \sqrt{2}\)

D. \(18\pi\)

E. \({9\pi}{\sqrt{2}}\)

Attachment:
2019-09-25_1548.png

The base forms an Isosceles right angle triangle (45 - 45 - 90) with the center of the circle
Let r be the radius of the circle
Base corresponds to the side opposite to 90 deg
--> \(\sqrt{2}r = 12\)
--> \(r = 6\sqrt{2}\)

Perimeter of 3/4th of the circle = \(3/4*2π*6\sqrt{2}\)
= \(9π\sqrt{2}\)

IMO Option C

Pls Hit Kudos if you like the solution

Could you please tell me, how do you know that the base forms a right angle at the center??
I know that it will form an isosceles triangle at the center, but how can we surely say that the angle subtended at the center is a right angle?
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Archit3110 thanks a lot. Got it now.
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