math

Question

two hundred multiples of seven are chosen at random, and 300 multiples of eight are chosen at random. approximately what percentage of the 500 selected numbers are odd?

Brent@GMATPrepNow · Answer

stephny wrote:two hundred multiples of seven are chosen at random, and 300 multiples of eight are chosen at random. approximately what percentage of the 500 selected numbers are odd?

This really isn't a GMAT-quality question, since it's possible that none of the selected numbers are odd. Or it's possible that half of the 200 multiples of 7 are odd, and half are even, in which case 100 of the 500 numbers are odd (20%). Or it's possible that all of the 200 multiples of 7 are odd, in which case 200 of the 500 numbers are odd (40%).

So, as you can see, the percentage of odd numbers can range from 0% to 40%.

Aside: All of the multiples of 8 will be even

I believe that the intent of this question is to ask, "What percent of the 500 selected numbers are EXPECTED TO BE odd?" However, as far as I know, the GMAT does not test the concept of "expected values," which makes this question out of scope.

Cheers,
Brent

Brent Hanneson - Creator of GMATPrepNow.com

Mathsbuddy · Answer

Brent@GMATPrepNow wrote:stephny wrote:two hundred multiples of seven are chosen at random, and 300 multiples of eight are chosen at random. approximately what percentage of the 500 selected numbers are odd? This really isn't a GMAT-quality question, since it's possible that none of the selected numbers are odd. Or it's possible that half of the 200 multiples of 7 are odd, and half are even, in which case 100 of the 500 numbers are odd (20%). Or it's possible that all of the 200 multiples of 7 are odd, in which case 200 of the 500 numbers are odd (40%). So, as you can see, the percentage of odd numbers can range from 0% to 40%. Aside: All of the multiples of 8 will be even I believe that the intent of this question is to ask, "What percent of the 500 selected numbers are EXPECTED TO BE odd?" However, as far as I know, the GMAT does not test the concept of "expected values," which makes this question out of scope. Cheers, Brent I think if the question were cleverly worded to address probability, it could become a GMAT style question. It seems to me that the word "approximate" was an attempt by the author to address this, although it was not the suitable adjective.

stephny · Answer

that was a GMAT question from 2011. thanks anyway, that was the same answer I got.

Brent@GMATPrepNow · Answer

stephny wrote:that was a GMAT question from 2011. thanks anyway, that was the same answer I got. Are you saying this is an official GMAT question? That seems unlikely. Cheers, Brent

Brent@GMATPrepNow · Answer

Mathsbuddy wrote: I think if the question were cleverly worded to address probability, it could become a GMAT style question. It seems to me that the word "approximate" was an attempt by the author to address this, although it was not the suitable adjective.

Perhaps.
Some answer choices would help too

Cheers,
Brent

Brent Hanneson - Creator of GMATPrepNow.com

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