closest value

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786: Master | Next Rank: 500 Posts; Posts: 119; Joined: Mon Jun 28, 2010 9:42 pmFollowed by: 1 member; Location: Pune; Thanked: 1 times; GMAT Score:660

by 786 » Mon Oct 03, 2011 1:56 am

The value of (9Ã—10^7)(9Ã—10^8) is closest to which of the following?

A. 10^16
B. 10^17
C. 10^56
D. 10^57
E. 10^58

[spoiler](9Ã—10^7)(9Ã—10^8) = 8.1 x 10^16
so closer to 10^17 ?[/spoiler]

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Source: Beat The GMAT — Problem Solving | Mon Oct 03, 2011 1:56 am

Geva@EconomistGMAT: GMAT Instructor; Posts: 905; Joined: Sun Sep 12, 2010 1:38 amFollowed by: 123 members; Thanked: 378 times; GMAT Score:760

by Geva@EconomistGMAT » Mon Oct 03, 2011 2:00 am

786 wrote:The value of (9Ã—10^7)(9Ã—10^8) is closest to which of the following?

A. 10^16
B. 10^17
C. 10^56
D. 10^57
E. 10^58

[spoiler](9Ã—10^7)(9Ã—10^8) = 8.1 x 10^16
so closer to 10^17 ?[/spoiler]

Makes Sense. 8.1 is close to 10, so what you have here is close to 10 x 10^16 = 10^17.

Geva
Senior Instructor
Master GMAT
1-888-780-GMAT
https://www.mastergmat.com

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Anurag@Gurome: GMAT Instructor; Posts: 3835; Joined: Fri Apr 02, 2010 10:00 pmFollowed by: 523 members; Location: Milpitas, CA; Thanked: 1854 times; GMAT Score:770

by Anurag@Gurome » Mon Oct 03, 2011 2:51 am

786 wrote:The value of (9Ã—10^7)(9Ã—10^8) is closest to which of the following?

A. 10^16
B. 10^17
C. 10^56
D. 10^57
E. 10^58

[spoiler](9Ã—10^7)(9Ã—10^8) = 8.1 x 10^16
so closer to 10^17 ?[/spoiler]

Multiplying (9 Ã— 10^7) and (9 Ã— 10^8) we get,
81 x 10^7 x 10^8
= 8.1 x 10^16, which is closer to 10^17

The correct answer is B.

Anurag Mairal, Ph.D., MBA
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Gurome, Inc.
1-800-566-4043 (USA)

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Jeff@TargetTestPrep: GMAT Instructor; Posts: 1462; Joined: Thu Apr 09, 2015 9:34 amFollowed by: 22 members; Location: New York, NY; Thanked: 39 times

by Jeff@TargetTestPrep » Thu Dec 14, 2017 3:47 pm

786 wrote:The value of (9Ã—10^7)(9Ã—10^8) is closest to which of the following?

A. 10^16
B. 10^17
C. 10^56
D. 10^57
E. 10^58

We can simplify the given expression.

(9 x 10^7)(9 x 10^8) = 9^2 x 10^15

We can immediately eliminate answer choices C, D, and E since powers of 10 in the order of 56, 57, or 58 is nowhere near the order of 15. We only need to decide between answer choices A and B. We note that 9^2 = 81 is closer to 100 than to 10; therefore, of the provided answer choices, 9^2 x 10^15 is closest to 10^17.

Answer: B

Jeffrey Miller
Head of GMAT Instruction
[email protected]

See why Target Test Prep is rated 5 out of 5 stars on BEAT the GMAT. Read our reviews

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