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by Anurag@Gurome » Mon May 21, 2012 7:28 pm
alex.gellatly wrote:Which of the following is equal to (2^k)(5^(k-1))

A. 2(10^(k-1))
B. 5(10^(k-1))
C. 10^k
D. 2(10^k)
E. 10^(2k-1)

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Alex, the expression is (2^k)(5^(k-1)), please check.

(2^k)(5^(k-1)) = [2 * 2^(k - 1)] * 5^(k - 1)
= [spoiler]2 * 10^(k - 1)[/spoiler]

The correct answer is A.
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by GmatKiss » Tue May 22, 2012 3:21 am
alex.gellatly wrote:Which of the following is equal to (2^k)(5^(K-1))

A. 2(10^(k-1))
B. 5(10^(k-1))
C. 10^k
D. 2(10^k)
E. 10^(2k-1)

Many Thanks
Easy way will be to sub value for k. Lets assume k=2
Then (2^k)(5^(K-1)) = 20 (Target)

Now sub k=2 in answer choices, to get to the target.

IMO: A
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by alex.gellatly » Tue May 22, 2012 6:15 pm
Sorry about the error. I've fixed it. Thanks again
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