0.99999999/1.0001 - 0.99999991/1.0003 =

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0.99999999/1.0001 - 0.99999991/1.0003 = [#permalink]

26 Dec 2012, 07:36

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35% (02:13) correct

64% (01:26) wrong

based on 6 sessions

\frac{0.99999999}{1.0001}-\frac{0.99999991}{1.0003}=

(A) 10^(-8)
(B) 3*10^(-8)
(C) 3*10^(-4)
(D) 2*10^(-4)
(E) 10^(-4)

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Re: 0.99999999/1.0001 - 0.99999991/1.0003 = [#permalink]

26 Dec 2012, 07:39

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Walkabout wrote:

\frac{0.99999999}{1.0001}-\frac{0.99999991}{1.0003}=

(A) 10^(-8)
(B) 3*10^(-8)
(C) 3*10^(-4)
(D) 2*10^(-4)
(E) 10^(-4)

\frac{0.99999999}{1.0001}-\frac{0.99999991}{1.0003}=\frac{1-10^{-8}}{1+10^{-4}}-\frac{1-9*10^{-8}}{1+3*10^{-4}}

Now apply a^2-b^2=(a+b)(a-b):

\frac{1-10^{-8}}{1+10^{-4}}-\frac{1-9*10^{-8}}{1+3*10^{-4}}=\frac{(1+10^{-4})(1-10^{-4})}{1+10^{-4}}-\frac{(1+3*10^{-4})(1-3*10^{-4})}{1+3*10^{-4}}=(1-10^{-4})-(1-3*10^{-4})=2*10^{-4}.

Answer: D.
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Re: 0.99999999/1.0001 - 0.99999991/1.0003 = [#permalink] 26 Dec 2012, 07:39

0.99999999/1.0001 - 0.99999991/1.0003 =

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0.99999999/1.0001 - 0.99999991/1.0003 =

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