GMAC software question

[jazzwillbe]

Here's a question from the official GMAT prep software.

The cost of each adult's ticket for a certain concert was $30, and the cost of each child's ticket for the concert was $24. If Hannah purchased tickets for this concert, what was the average(arithmetic mean) cost per ticket?

(1) Hannah purchased twice as many childrens tickets as adult's tickets

(2) Hannah purchased 4 childrens tickets.

Data sufficiency questions guys.

The answer is (A). Am I missing something here.

Thanks
J

[jazzwillbe]

Mark,
Thanks for the post. I do agree that 1st statement is enough. But the 2nd statement says that she bought 4 childrens tickets only, which means that the average is 24.

I think there is an error in the question

Thanks

[jayhawk2001]

Jazzwillbe, I don't think we can make the assumption that "only" 4
children tickets were purchased.

(2) just says that Hannan purchased 4 children tickets and does not
mention how many adult tickets were purchased.

[getso]

Hello Friends,

I'm reopening this post.

Could anybody give the correct explaination to the question posted.

Thanks,
Shobha

[bigmikefr]

The average cost per ticket is (30A+24C)/A+C, where A and C stand for the number of adult tickets and the number of children tickets respectively

(1) Here they tell us that A= 2C. So you can plug A=2 & C=1; then try A=4 & C=2. You will find that on both occasions, the mean is 28 and it does not change. SUFFICIENT

(2) This tell us C=4. But with no further information, we cannot calculate the average. INSUFFICIENT

So A only

[aspirant1]

Could anyone pls help on the assumption here...

b) talks about only child's ticket.

My thought would be, we can still calculate the average cost of the ticket. BECAUSE : question does not talk about number of adult tickets purchased by Hannaf, But only the value of tickets. so the assumption would be average of whatever the ticket she has purchased.

Is this not a right assumption...? pls help

[kimjone]

Could anyone pls help on the assumption here...

b) talks about only child's ticket.

My thought would be, we can still calculate the average cost of the ticket. BECAUSE : question does not talk about number of adult tickets purchased by Hannaf, But only the value of tickets. so the assumption would be average of whatever the ticket she has purchased.

Is this not a right assumption...? pls help

I agree with you aspirant, and your train of thought. I chose D because I thought both were sufficient..

[upkarsgrewal]

Same here. I chose D. The given information for statement 2 is that she bought 4 Childrens Tickets. That means it can be solved. How is the reader supposed to assume that additional tickets could have been bought. The GMAC is wrong on this question. It's data sufficiency. You are given enough data in statement 2 to decide the average price per tickets. I picked D and I feel its not wrong in any way.

[lunarpower]

first --
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; please note that doing so is a complete waste of your time and effort. i.e., exactly 0% of the time that you spend posting "isn't this official answer wrong?" is productive, and exactly 100% of that time is wasted.

"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 suddenly find it much easier to understand the format, style, and conventions of the official problems if you dispose of the idea that they might be wrong.

--

second:

on this problem, if you know the conventions by which gmac creates data sufficiency problems, you can actually figure out that the second statement CAN'T mean "4 children's tickets and 0 adult tickets".
here's how:
on an official DS problem, the two numbered statements will NEVER contradict each other. if you think that the two numbered statements are mutually contradictory, your interpretation of at least one of them is definitely wrong.

in this problem, if you interpret the second statement as "4 children's and 0 adult tickets", then that contradicts the first statement, proving that your interpretation of the second statement must be wrong.

--

in any case, once you get over the "isn't this wrong" feeling (no, it's not wrong), you'll learn a valuable lesson about the way GMAC (and the english language in general) frames quantity statements. as another example, if i tell someone "i have two sons", this statement does not mean that i don't have any daughters.

don't question the official answers! LEARN from them!