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oquiella: Master | Next Rank: 500 Posts; Posts: 164; Joined: Tue May 12, 2015 9:06 am; Thanked: 3 times

by oquiella » Thu Dec 24, 2015 8:37 am

The productt of all the prime numbers less than 20 is closest to which of the followig powers of 10?

A. 10^9
B. 10^8
C. 10^7
D. 10^6
E. 10^5

Answer: C

Is there a quicker way to do this without multiplying all the prime numbers out?

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Source: Beat The GMAT — Problem Solving | Thu Dec 24, 2015 8:37 am

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by [email protected] » Thu Dec 24, 2015 9:01 am

Hi oquiella,

Any time a Quant question 'looks like' it will take a lot of calculations to solve, there's almost always some type of pattern that you can take advantage of (to avoid most of that math). For this prompt, you really just have to 'organize' the math in a particular way. There's a discussion on that idea here:

https://www.beatthegmat.com/product-of-a ... 16565.html

GMAT assassins aren't born, they're made,
Rich

Contact Rich at [email protected]

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