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# A lighthouse emits a light that can be seen for 60 miles in

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A lighthouse emits a light that can be seen for 60 miles in [#permalink]  03 Dec 2019, 02:50
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33% (00:27) correct 66% (00:21) wrong based on 9 sessions
A lighthouse emits a light that can be seen for 60 miles in all directions. If the intensity of the light is strengthened so that its visibility is increased by 40 miles in all directions, by approximately how many square miles is its region of visibility increased?

A. 6,300

B. 10,000

C, 10,300

D. 20,000

E. 31,400

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[Reveal] Spoiler: OA

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Re: A lighthouse emits a light that can be seen for 60 miles in [#permalink]  04 Dec 2019, 00:53
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Initially the coverage area had a radius of 60miles. So the area is A1 = pi*(60^2)
Later, the radius increased by 40 miles. Now new radius is 100 and new area A2 = pi*(100^2)
Area increased is A2-A1. That approximates to 20,000 (option D)
Re: A lighthouse emits a light that can be seen for 60 miles in   [#permalink] 04 Dec 2019, 00:53
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