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# The radius, R, of a larger circle is 555 centimeters. The radius, r,..

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Director
Joined: 11 Feb 2015
Posts: 617

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06 Oct 2018, 10:57
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Difficulty:

35% (medium)

Question Stats:

62% (01:12) correct 38% (01:21) wrong based on 13 sessions

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The radius, R, of a larger circle is 555 centimeters. The radius, r, of a smaller circle is 55 centimeters. Which of the following properly expresses, in square meters, the difference between the areas of the two circles? (Note: 1 meter = 100 centimeters)

A) 30.5 $$\pi$$

B) 305 $$\pi$$

C) 3050 $$\pi$$

D) 30,500 $$\pi$$

E) 305,000 $$\pi$$

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06 Oct 2018, 11:46
By Using formula $$\pi(R^2 - r^2)$$ ,We can find the difference in areas.

Put $$R=555$$ and $$r = 55$$ in above formula .Use identity $$a^2$$ - $$b^2$$ = $$(a+b)(a-b$$)

We will get $$305000$$$$\pi$$

Now this is in $$cm^2$$.We need area in $$m^2$$ .So we have to divide area by $$100$$ twice as we have multiplication of $$cm*cm$$($$cm^2$$) in units.

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Re: The radius, R, of a larger circle is 555 centimeters. The radius, r,.. &nbs [#permalink] 06 Oct 2018, 11:46
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