According to surveys by the National Institute on Drug Abuse, about 20

For ex: The percentage of increase in new CPU’s performance is twice the number to its predecessor’s ones.

(A) doubling those reported in the 1977 survey [Doubling incorrectly modifying the meaning – eliminate it]

(B) to double the number the 1977 survey reported [This is changing the meaning – eliminate it]

(C) twice those the 1977 survey reported [Number is compared people – eliminate it]

(D) twice as much as those reported in the 1977 survey [Number is compared people – eliminate it]

(E) twice the number reported in the 1977 survey [ The number is compared correctly – hold it]

Answer: E

Answer option E.
Anirudh, both "Doubling" & "to double" when used sound as if 'about 20 percent of young adults' were causal to the increase in numbers. What essentially the author wants to mean is that tha 'number of young adults using cocaine' 'now' compared to '1970 survey' is double.

Option E takes care of this error making it more precise.

You might want to look at this sentence from OG11 for more explanation involving such usage..

The gyrfalcons, an arctic bird of prey, has survived a close brush with extinction; its numbers are now five times greater than when the use of DDT was sharply restricted in the early 1970s.

According to surveys by the National Institute on Drug Abuse, about 20 percent of young adults used cocaine in 1979, doubling those reported in the 1977 survey.

(A) doubling those reported in the 1977 survey - '20% percent' [number] is compared to 'young people'
(B) to double the number the 1977 survey reported - surveys dont report.
(C) twice those the 1977 survey reported - '20% percent' [number] is compared to 'young people'
(D) twice as much as those reported in the 1977 survey - '20% percent' [number] is compared to 'young people'
(E) twice the number reported in the 1977 survey - '20% percent' [number] is correctly compared to 'number'

I am not an expert... But this is how I got to the answer...

51. According to surveys by the National Institute on Drug Abuse, about 20 percent of young adults used cocaine in 1979, doubling those reported in the 1977 survey.
(A) doubling those reported in the 1977 survey -- What is those pointing to?? Replace "20 percent of young adults" in the later...and not proper
(B) to double the number the 1977 survey reported -- not proper
(C) twice those the 1977 survey reported
(D) twice as much as those reported in the 1977 survey -- What is those
(E) twice the number reported in the 1977 survey -- correct


Still, I am looking forward from the experts on their approach

hi ankur,

option E :==>NUMBERS ARE COMPARED TO NUMBERS AND NOT PERSON TO NUMBERS.

lets see: 20 percent of X=RESULT==>If you see..result is always a numerical value....whenever there is mathematics ...it is going to give you value.
for example: if you have 100 gm protein==>if i say 20 percent of protein you will burn while running==>what does this mean=>20 gm protein you will utilise while burning===>thats a numerical value===>so takeaway is that whenever you have PERCENT OF SOMETHING===>then you should always compare to numerical thing..and not to any other thing.

moreover in option C THOSE ==>it ise referring to children so we cant compare number with children.

hope it helps

A,C and D are eliminated because we are trying to compare the percentage of young adults reported for cocaine use. We are not comparing the number of young adults or young adults between 1977 and 1979; we are rather comparing the percentage, which is a number. Meaning the sentence is reporting percentage as a number, which is 20 for the year 1979. The sentence means to say that the percentage reported in 1977 was 10 percent.

OC: E

According to surveys by the National Institute on Drug Abuse, about 20 percent of young adults used cocaine in 1979, doubling those reported in the 1977 survey.

First of all, there is no cause and effect and the next sentence fragment is just to add comparison between the numbers in 1979 and 1977.

A. doubling those reported in the 1977 survey -> Doubling is a verbing modifier and suggest that sentence is an effect of the previous clause which is not the case.

B. to double the number the 1977 survey reported -> to double shows intent. The sentence just shows a comparison and doesn't say that anything is done to double anything

C. twice those the 1977 survey reported -> those refer to adults whereas we are comparing number of adults in 1979 and 1977.

D. twice as much as those reported in the 1977 survey -> similar issue as option C)

E. twice the number reported in the 1977 survey -> twice the number is the correct comparison.

Twice is an adjective or an adverb which can modify a noun or an adjective wheras double can act as as a verb or or an adjective.

A. doubling those reported in the 1977 survey
awkward structure, comma+ing serves as a noun modifier. But since the comma+ing modifier must associate with SV of the clause that it modifies, in our case it does not make any sense.

B. to double the number the 1977 survey reported
to+verb is used to show purpose. This choice alters the meaning of the sentence. Now it implies that 20% of young adults used cocain so that to double the number… illogical.

C. twice those the 1977 survey reported
2 independent clauses connected only by a comma

D. twice as much as those reported in the 1977 survey
“as much as” used with people. Much is used with uncountable nouns only.

E. twice the number reported in the 1977 survey
Correct answer choice. Now the underlined portion serves as noun (twice the number) + noun modifier (reported)

According to surveys by the National Institute on Drug Abuse, about 20 percent of young adults used cocaine in 1979, doubling those reported in the 1977 survey.(

(A) doubling those reported in the 1977 survey - DOUBLING has distorted the actual meaning of the sentence.

(B) to double the number the 1977 survey reported - the 20 % have intentionally doubled the number, which is not the actual meaning

(C) twice those the 1977 survey reported - Wrong comparison - Number compared to people.

(D) twice as much as those reported in the 1977 survey - Wrong Comparison - Same as C

(E) twice the number reported in the 1977 survey - Number Compared to Number. - CORRECT.

According to surveys by the National Institute on Drug Abuse, about 20 percent of young adults used cocaine in 1979, doubling those reported in the 1977 survey.

Those is referring to adults or 20 percent of young adults on the whole?
zillion thanks in advance

Can someone please explain me the usage of 'double' and 'twice' on the GMAT and help me understand the difference between them?

Do this question again.

It is clear that in this question we are modifying the "20 percent of the adults". how can you modify percent to the number? Please explain. daagh sir, GMATNinja.

The expression "about 20 percent of young adults" refers to a NUMBER of people: there is some total number of young adults, and we are talking about 20 percent of that total number.

In other words, 20 percent of [the first number] equals [the second number], and it's okay to refer to twice [the second number].

Of course, this question was written in the 80s, so I wouldn't lose much sleep over it.

(A) doubling those reported in the 1977 survey
those refers to young adults, but the comparison here is about number

(B) to double the number the 1977 survey reported
participle usage is incorrect here

(C) twice those the 1977 survey reported
those refers to young adults, but the comparison here is about number

(D) twice as much as those reported in the 1977 survey
those refers to young adults, but the comparison here is about number

(E) twice the number reported in the 1977 survey
no error

girisshhh84 But, the option E is talking about number where as it is mentioned 20%. Is the comparison correct?

daagh Please help.

Twice the number is the number of cases reported in 1977 which was half of that of 1979. Not the other way round!
20% is the number reported in 1979 which is double of that of reported in 1977.

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ReedArnoldMPREP - how would you pick (e) over (c) ?

too me (c) seems okay.

here is my analysis on (c)

people keep saying (c) has a comparison problem - i am not sure i see it
- i dont believe "twice or double" are comparison markers to begin with

there is a clear antecedent for "those"
-- the antecedent of "those" is 20 % of adults (20 % of adults is plural per my understanding)
-- analogy : 10 % of girls in class 1A are taller than those in class 1b

people are saying (c) has a pronoun issue
- i dont see why those is wrong == those has a modifier in front
- the modifier in front of those is the "the 1977 survey reported"
- that way the those is not a stand-alone pronoun (those is attached to a modifer)