double vs twice

[herogmat]

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

What is the approach to choose between 'double' and 'twice' ?
How to choose between C and E ?

--hg

[mangipudi]

> What is the approach to choose between 'double' and 'twice' ?
'Double the number' and 'twice the number' are both valid.
However, the answer choice with double the number has other problems.

> How to choose between C and E ?
(C) twice those the 1977 survey reported
'Those' refers to 'young men'. You cannot have 'twice young men'. You have 'twice the number of young men' .

[selva.e]

Twice is always used for comparison.

For example,
USA has roughly twice as many people as India (does).

Whereas, double is mostly used as adjective/noun/participle

The number of people flying first class on domestic flights rose sharply in 1990 , doubling the increase of the previous year.
doubling the increase of
doubling that of the increase in
double as much as the increase of
twice as many as the increase in
twice as many as the increase of

Hope you got it!!

[d_taneja]

In C and E--> E is correct because in C it says that "twice those the 1977 survey reported" Two error..first one that it is not parallel with "in 1977" before comma
2nd it can not be twice of young adults but it can be twice the no of those surveyed in 1977

[esledge]

In C and E--> E is correct because in C it says that "twice those the 1977 survey reported" Two error..first one that it is not parallel with "in 1977" before comma
2nd it can not be twice of young adults but it can be twice the no of those surveyed in 1977

The parallelism you see between "in 1977" and "in 1979" might be false parallelism.
That is, I think you don't really need "in...in" parallelism to have a correct answer. For example, I think the following sentence would be OK:

According to a 1979 survey by the National Institute on Drug Abuse, about 20 percent of young adults used cocaine that year, twice the number reported in the 1977 survey.

However, the "in" split between C and E is significant for another reason:

(C) "...the 1979 survey reported..." makes the survey the subject of the verb reported. There's a logical flaw--surveys don't report. People can report, using survey data.

(E) "...reported (by someone) in the 1977 survey..."

[herogmat]

Thanks Emily .

[khandelwal_mayank]

Hey I chose D as an answer.
Can someone explain why E is better than D
I thought that number is not the same as percentage so eliminated E

[gmat.cracker24]

I guess for percentage vs. number debate, a analogy that i can think off is :
Country's GDP has increased by 50%, a number previously thought unlikely.
I believe if the GDP rises from 7% to 14% , the phrase set off by commas modifies 14.
However for D "those" seems a issue

[jnelson0612]

Can anyone provide the original source for this question?

[gmatango]

I just read a detailed post about the usage of "twice". Link below:

http://www.manhattangmat.com/forums/the-number-of-people-flying-first-t5600.html

Then upon landing on this question I see "twice" used here incorrectly as an appositive.

Could instructors please explain where am I going wrong ?

Thanks!

[jnelson0612]

We still need to obtain an original source for this question, along with the original answer, before we discuss further.

[ntr1989512]

We still need to obtain an original source for this question, along with the original answer, before we discuss further.

the source come from prep!
in addition, i was stuck by E, since i remember ron say the form of "twice as many\much as" can only modify the noun that comes immediately before the comma. and in E "twice the number reported in the 1977 survey" is followed by "in 1979", so "twice the..."should modify 1979. it doesn't make sense. so why E is right?

if you're going to say COMMA + "twice as many as...", then that's incorrect unless there's actually a quantity in front of the comma.
e.g.
last year i read 40 books, twice as many as i read in the preceding year
--> correct
last year the number of books i read increased dramatically, twice as many as i read in the preceding year
--> incorrect.

&

here's the basic idea:

if you say "twice as many", then this construction should be paired with a countable noun.
e.g., twice as many dogs --> "dogs" is a countable noun

if you said "twice as much", then this construction should be paired with an uncountable noun.
e.g., twice as much water --> "water" is an uncountable noun

if the noun in question is already an explicitly numerical quantity, then you should use neither "much" nor "many". instead, you should just use "twice" or "double" by itself.
e.g., twice the increase --> "increase" is an explicitly numerical quantity

these rules are followed pretty closely.
so, for instance:
twice as much water --> correct, since "water" is an uncountable noun (but is not an explicitly numerical quantity)
twice the water... --> incorrect, since water is not a numerical quantity

twice as much as the increase... --> incorrect; redundant
twice the increase... --> correct.

[ntr1989512]

i very sorry to dig out this thread, becasue i think every master in MANHATTAN omit this thread..hope your answer.thanks

[nhsumon_loll]

my choice is E...caz in option C it mislead the comparison where as in option E it makes clear...

[tim]

"prep" doesn't mean anything to us; we still need a source. and i'm not sure what the point of ntr's post on May 23 was..