Africa's black rhino population

[rakov.a3]

Africa's black rhino population in the mid-1970's numbered about 20,000, ten times the estimated population of 2,000 in 1997.

(A) the estimated population
(B) that of their estimated population
(C) more than the population's estimated amount
(D) more black rhinos than their population estimate
(E) more than that of their population's estimated amount

I exclueded C & E because of wrong usage of the word "amount" and B & D because of absence of the proper antecedant for pronoun "their".
However I still doubt whether this sentece uses correct comparison of the population in different years. Wouldn't it be more grammatically correct to say "more than the estimated population".
Please explain. THANKS!!!

P.S. OA is A.

[RonPurewal]

However I still doubt whether...

officially correct answers are correct!
do not question officially correct answers!
far too many students on this forum make the mistake of questioning the correct answers; to do so is to waste your time and effort.

"is this correct?" is never a productive question to ask about one of GMAC's correct answers -- the answer is always yes.
"is this wrong?" / "is this X type of error?" is never a productive question to ask about one of GMAC's correct answers -- the answer is always no.

instead, the questions you should be asking about correct official answers, if you don't understand them, are:
"why is this correct?"
"how does this work?"
"what understanding am i lacking that i need to understand this choice?"

this is a small, but hugely significant, change to your way of thinking.
you will find it much easier to understand the format, style, and conventions of the official problems if you retire the idea that they might be wrong.

--

"X is # times Y" is a perfectly valid construction, and "X is # times more than Y" is another perfectly valid construction. they're not mathematically the same, but the mathematical difference is irrelevant on SC.

[thanghnvn]

why C is wrong?

because it is wordy and has no meaning of "ten"???

pls, explain

[RonPurewal]

why C is wrong?

because it is wordy and has no meaning of "ten"???

pls, explain

"Wordy" is not an error. (if you have to guess, then you can use "wordiness" as a guideline -- but every wrong answer has to have some aspect that's actually wrong.)

In that choice --

* "Amount" is incorrect. Because rhinos can be counted, it needs to be "number" instead.

* "Population" already represents the number of rhinos. So, if "population" is there, the use of "number" or "amount" is redundant.