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# Which of the following is closest to 10^180 10^30 ? A.

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Manager
Joined: 03 Oct 2008
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Which of the following is closest to 10^180 10^30 ? A. [#permalink]

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09 Oct 2008, 05:38
This topic is locked. If you want to discuss this question please re-post it in the respective forum.

Which of the following is closest to 10^180 – 10^30 ?

A. 10^210
B. 10^180
C. 10^150
D. 10^90
E. 10^6
Manager
Joined: 22 Sep 2008
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09 Oct 2008, 05:50
1
KUDOS
10^1 = 10...1 digit

10^2 = 100 .. 3 digits

10^3 = 1000 ... 4digits

10^4 = 10,000 ... 5digits

10^4 - 10^2 = 10,000 - 100 = 9900 .. which is nearar to 10^4 or 10^2 (10^2-1)= 100(100-1) = 9900, which ever way you find comfortable but it will be nearar to 10^4

apply same thing here
10^30(10^150-1) will be nearar to 10^180..

Vishal Shah
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09 Oct 2008, 07:14
albany09 wrote:
Which of the following is closest to 10^180 – 10^30 ?

A. 10^210
B. 10^180
C. 10^150
D. 10^90
E. 10^6

10^180 – 10^30 = 10^30(10^150 - 1) APPROX = 10^30(10^150) = 10^180

b
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Joined: 17 Jun 2008
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09 Oct 2008, 07:27
yezz wrote:
albany09 wrote:
Which of the following is closest to 10^180 – 10^30 ?

A. 10^210
B. 10^180
C. 10^150
D. 10^90
E. 10^6

10^180 – 10^30 = 10^30(10^150 - 1) APPROX = 10^30(10^150) = 10^180

b

10^180 – 10^30 nearly = 10^180 hence IMO B
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Re: math   [#permalink] 09 Oct 2008, 07:27
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