GmatKiss wrote:The product of all the prime numbers less than 20 is closest to which of the following powers of 10?
A.10^5
B.10^9
C.10^7
D.10^6
E.10^8
Since the answer choices are VERY far apart, we can BALLPARK.
For every value that we round UP, we should compensate by rounding another value DOWN.
2*3*5*7*
11*13*
17*19
210 *
10*15 *
15*20
200*
150*
300 = 9,000,000.
The closest power of 10 = 10,000,000 = 10^7.
The correct answer is
C.
Last edited by
GMATGuruNY on Tue Mar 26, 2013 5:28 am, edited 1 time in total.
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