Data Sufficiency

What is the probability that on a given workday Mr. Jonathan dresses in formals, travels by car to his
office, and drinks a coffee there?
(1) Jonathan dresses in formals on alternate days, and drinks coffee each day he wears formals.
(2) Jonathan goes to his office by car 3 of every 5 days.

Source:Nova DS prep
OA later

What is the probability that on a given workday Mr. Jonathan dresses in formals, travels by car to his
office, and drinks a coffee there?
(1) Jonathan dresses in formals on alternate days, and drinks coffee AT HIS OFFICE each day he wears formals.
(2) Jonathan goes to his office by car 3 of every 5 days.

Hi frank1!

The problem is with the problem itself... this is one of the cases when we do not know if the creator of the problem is trying to trap us or if he/she was only less careful than he/she should... I will admit the first option!

(I added something in the question stem, but even so there are problems... see below!)

Answer (with considerations above and below): E

(1) BIFURCATES:

> If Jonathan NEVER goes to his office by car, then the probability asked is certainly ZERO.
> If Jonathan ALWAYS goes to his office by car, then the probability asked is certainly NOT ZERO.

Comment: the usual "is insufficient because I know nothing about the car" is not nice. What I did above is "explore" this fact to GUARANTEE (1) is not sufficient.

(2) BIFURCATES:

> If Jonathan NEVER dresses in formals and NEVER drinks coffee at the office, the answer is ZERO.
> If Jonathan ALWAYS... and ALWAYS... , the answer is NOT ZERO.

(1+2) BIFURCATES:

> If Jonathan drinks coffee AT HIS OFFICE each day he wears formals AND ONLY at these days, the answer is something.
> If Jonathan drinks coffee AT HIS OFFICE each day he wears formals BUT ALSO in additional days, the answer is different.

Obs.: why do I believe that this is what the creator of the problem had in mind? Because to solve the problem mathematically, admitting some additional info, would be better served in a Problem Solving mind, not in a Data Sufficiency one... (my opinion and GMAT teaching experience)

Best Regards,
Fábio.

frank1 wrote:What is the probability that on a given workday Mr. Jonathan dresses in formals, travels by car to his
office, and drinks a coffee there?
(1) Jonathan dresses in formals on alternate days, and drinks coffee each day he wears formals.
(2) Jonathan goes to his office by car 3 of every 5 days.

Source:Nova DS prep
OA later

I have NOVA's 2008 edition with me, and I couldn't find this question anywhere in there. I solemnly believe that this question is certainly missing a thing even if [spoiler]E[/spoiler] is its answer. Please re-check, till then


[spoiler]it's E[/spoiler]

sanju09 wrote: I have NOVA's 2008 edition with me, and I couldn't find this question anywhere in there. I solemnly believe that this question is certainly missing a thing even if [spoiler]E[/spoiler] is its answer. Please re-check, till then
[spoiler]it's E[/spoiler]

It is from Nova Gmat data prep 2009 edition
Its explanation

Statement (1): Jonathan dresses in formals on
alternate days, and drinks coffee each day he wears
formals.
Note: It is alternate days, not just alternate
workdays. Jonathan dresses in formals on alternate
days; so not on each alternate workday. In other
words, we are not sure which set of alternate days
of the week; so we are not sure about the schedule
of working days; So, we cannot get the probability
of Jonathan being dressed in formals on a given
workday. So, we cannot get the probability of
dressing in formals ... blah, blah, blah ... on a
given workday.
On each day, he wears formals, and he drinks
coffee, but we are not given "Where?" whether it is
in his office or not. So, the statement is not
sufficient.

Statement (2): Jonathan goes to office by car 3 of
every 5 days.
Jonathan goes by car (not sure if it is his car; we
need the probability of traveling by his car.)
The statement is not sufficient.

SO E.

Uau, this is probably one of the stupidiest problems/explanations I´ve already seen... and man, I´ve already seen too many stupid things like that!

(Do not worry about this kind of sillyness in the GMAT, frank1. They respect your intelligence!)

fskilnik wrote:Uau, this is probably one of the stupidiest problems/explanations I´ve already seen... and man, I´ve already seen too many stupid things like that!

(Do not worry about this kind of sillyness in the GMAT, frank1. They respect your intelligence!)

i like this sentence " they respect your intelligence" lol .... nice!

Statement 1. Jonathan dresses in formals on alternate days, and drinks coffee each day he wears formals.
Here the no of workdays a week is not given and also we don't know the no of days he goes to office by his car. So, we can't find the probability by statement 1 alone. Hence, Insufficient.
Statement 2. Jonathan goes to his office by car 3 of every 5 days.
Statement 2 doesn't mention the no of workdays Jonathan wear formals and drinks coffee in the office.
Hence, Insufficient.
Statement 1 & 2 together. Combining both the statements, we are still unaware of no of workdays in a week and if he number of days in which Jonathan drinks coffee in the office. It is not made clear if he drinks coffee in the office or somewhere else. Hence, Insufficient.