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closest value

by 786 » Mon Oct 03, 2011 1:56 am
The value of (9×10^7)(9×10^8) is closest to which of the following?

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

[spoiler](9×10^7)(9×10^8) = 8.1 x 10^16
so closer to 10^17 ?[/spoiler]
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by Geva@EconomistGMAT » Mon Oct 03, 2011 2:00 am
786 wrote:The value of (9×10^7)(9×10^8) is closest to which of the following?

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

[spoiler](9×10^7)(9×10^8) = 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.
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by Anurag@Gurome » Mon Oct 03, 2011 2:51 am
786 wrote:The value of (9×10^7)(9×10^8) is closest to which of the following?

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

[spoiler](9×10^7)(9×10^8) = 8.1 x 10^16
so closer to 10^17 ?[/spoiler]
Multiplying (9 × 10^7) and (9 × 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.
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by Jeff@TargetTestPrep » Thu Dec 14, 2017 3:47 pm
786 wrote:The value of (9×10^7)(9×10^8) 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

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Head of GMAT Instruction
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