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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 _________________

This is a comparison issue; so what are being compared? A number (that is 20 percent which is a quantum and hence singular) has to be compared with some thing similar. Therefore, the other arm of the comparison should also indicate a quantum number. The spoil - sport is the ambiguous those in A,C and D. In B to double the number gives an absurd dimension that the 20 percent went on mission to double the number

Choice E succinctly compares the 20 percent with twice the number. _________________

According to surveys by the National Institute on Drug [#permalink]
19 May 2012, 03:22

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 (B) to double the number the 1977 survey reported (C) twice those the 1977 survey reported (D) twice as much as those reported in the 1977 survey (E) twice the number reported in the 1977 survey

Re: Twice or Double [#permalink]
19 May 2012, 03:27

1

This post received KUDOS

The comparison has to be like. As the number (or percentage) of adults is being adults is being reported in 1979, it must be compared to a number (and not to the number of adults) in 1977.

Re: Twice or Double [#permalink]
20 May 2012, 08:18

nikhilarora88 wrote:

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 (B) to double the number the 1977 survey reported (C) twice those the 1977 survey reported (D) twice as much as those reported in the 1977 survey (E) twice the number reported in the 1977 survey

A, B and C are obviously out. Between D and E, D uses 'much' and this is used for comparing indefinite amounts e.g. too much sugar in the tea. Since we have a definite number here, it has to be E

Re: Twice or Double [#permalink]
22 May 2012, 20:31

nikhilarora88 wrote:

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 (B) to double the number the 1977 survey reported (C) twice those the 1977 survey reported (D) twice as much as those reported in the 1977 survey (E) twice the number reported in the 1977 survey

A: doubling those reported is not right as it is trying to double those young adults... HENCE WRONG B: both segments are incomplete.. about 20% percent of young adults used cocaine in 1979 and to double the number the 1977 survey reported.. are we trying to double the number survey reported? hence WRONG C: TWICE THOSE, is 1979 twice those? WRONG D: TWICE as much as those reported.. here again 1979 is talked about hence WRONG E: here it clearly compares 20% with the twice the number... hence CORRECT

may be i am wrong in understanding, can somebody help _________________

Regards, Harsha

Note: Give me kudos if my approach is right , else help me understand where i am missing.. I want to bell the GMAT Cat

Re: Twice or Double [#permalink]
22 May 2012, 22:32

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.

The above red one is being compared.

(A) doubling those reported in the 1977 survey wrong comparison. 20 percent of young adults vs a number of those reported

(B) to double the number the 1977 survey reported to double, infinite form is wrong.

(C) twice those the 1977 survey reported wrong comparison. 20 percent of young adults vs a number of those reported

(D) twice as much as those reported in the 1977 survey wrong comparison. much is non-countable.

(E) twice the number reported in the 1977 survey correct. _________________

Luck is the additional surplus on the way to one's constant effort.

Re: According to surveys by the National Institute on Drug [#permalink]
29 Aug 2012, 09:13

Okay , let me put a bit of math in here. If option "D" were "twice as MANY as those reported in the 1977 survey" would it be right?

I know many people up here said that here the comparison is between 20% and X%. BUT, and I may be wrong, What is 20% of 100 people? is it 20 people or just the number 20? We often say statements such as "50% of people are rich". We mean a certain number of PEOPLE are rich and not that the NUMBER is rich. If we follow the same analogy here, does it make the modified option "D" correct?

Would be glad if someone comments on this one. _________________

According to surveys by the National Institute on Drug Abuse [#permalink]
10 Jul 2013, 07:17

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 B. to double the number the 1977 survey reported C. twice those the 1977 survey reported D. twice as much as those reported in the 1977 survey E. twice the number reported in the 1977 survey

Hi All, (What I know) Twice is used for following comparison where some numbers or quantity is mentioned.

Ex: He has got 50 balls,twice as many as I have. USA has roughly twice as many people as India (does).

Similarly in the above example 20% is twice that present in 1977 Am I correct in understanding the usage of twice or any other way to find the usage.

If the options would have been

D1. twice as many as reported in the 1977 survey D2. twice as many as those reported in the 1977 survey

Is D1/D2 correct?I do understand 20% is compared to a number in 1977 which is twice.Why can't we say 20 adults are twice that present in 1977. Is much used for % ?

Apology if I have not asked the question correct way.I want to clear my understanding of twice & much.

Last edited by Zarrolou on 10 Jul 2013, 07:20, edited 2 times in total.

Re: According to surveys by the National Institute on Drug [#permalink]
10 Jul 2013, 22:58

(C) twice those the 1977 survey reported Why is this wrong (E) twice the number reported in the 1977 survey here the persons are compared to numbers, why is this correct

Re: According to surveys by the National Institute on Drug [#permalink]
10 Jul 2013, 23:36

1

This post received KUDOS

ankurgupta03 wrote:

(C) twice those the 1977 survey reported Why is this wrong (E) twice the number reported in the 1977 survey here the persons are compared to numbers, why is this correct

Some one please explain

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 _________________

When you want to succeed as bad as you want to breathe ...then you will be successfull....

Twice vs Double---Need ur thoughts. [#permalink]
20 Jul 2013, 06:27

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 (B) to double the number the 1977 survey reported (C) twice those the 1977 survey reported (D) twice as much as those reported in the 1977 survey (E) twice the number reported in the 1977 survey

Please find my understanding and let me know my mistakes.

Lets say there are 100 adults in 1977 and 1979. About 20% is 20 in 1979 and it must be 10 in 1977. if I re frame the question :

(D)about 20 adults used cocaine in 1979,twice 10 adults reported in 1977 survey. (E)about 20 adults used cocaine in 1979,twice 10 reported in 1977 survey.

So whyn't D be a better answer.Because 20 adults is twice that of 10 adults reported in survey.

Last edited by Narenn on 20 Jul 2013, 07:01, edited 1 time in total.

Merging Similar Topics Refer to the Brian's post in the similar thread http://gmatclub.com/forum/according-to-surveys-by-the-national-institute-on-drug-19660.html#p820081