Expert reply here:

https://www.beatthegmat.com/representati ... 39717.html

reddox wrote:Representation in a local community board is based on the community's population, with 25 board members representing the first 500,000 people, and each additional board member representing an additional 30,000 people. Is the population of the town less than 500,000?

(1) There were 23 members on the community board.

(2) If the population were three times as large, the community board would have had 51 members.


[spoiler]I answered 'B' because I assumed its exactly 500000 for upto 25 members. So this could mean population <= 500000. But OA is D[/spoiler]

For every first 20,000 population there would be one representative. When the population reaches 500,000, there would be 25 members. Then onwards, for every additional population of 30,000 there would be a representative. If the population is 500,000 there must be exactly 25 members. If the population less than 500,000 there must be less than 25 members.

(1) There were 23 members on the community board. >> Population is 23*20,000. Less than 500,000. SUF

(2) If the population were three times as large, the community board would have had 51 members. >> Population is more than 500,000. SUF

Ans D. Although it's not a GMAT standard question because both statements lead to different populations.