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dianapaolasanchez
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Post subject: Delivery order of desk chairs...Prep 2 Math  Posted: Sun Dec 13, 2009 9:20 pm |
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Posts: 21
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The cost of delivery for an order of desk chairs was $10.00 for the first chair, and additional $1.00 for each additional chair in order. If an office manager placed and order for n desk, is n>24?
1) The delivery cost for the order totaled more than $30.00
2) The average (arithmetic mean) delivery cost per chair of the n chairs was $1.36
I think is D, I am not sure, somebody can explain me? Thanks
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jerly_vivek
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Post subject: Re: Delivery order of desk chairs...Prep 2 Math Posted: Sun Dec 13, 2009 11:18 pm |
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Posts: 19
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IMO B.
I is not sufficient.
22 chairs, less than 24 : total cost $31, greater than 30.
25 chairs, more than 24 : total cost $34, greater than 30
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shrads.jp
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Post subject: Re: Delivery order of desk chairs...Prep 2 Math Posted: Mon Dec 14, 2009 12:05 am |
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jerly_vivek wrote: IMO B.
I is not sufficient.
22 chairs, less than 24 : total cost $31, greater than 30.
25 chairs, more than 24 : total cost $34, greater than 30 i want to just correct to wht is written... It should be 22 chairs,less than 24 : total cost $29.92, less than 30 the other statement is correct Then the answer can be inferred as B
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mikrodj
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Post subject: Re: Delivery order of desk chairs...Prep 2 Math Posted: Tue Dec 15, 2009 6:16 am |
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I also think the correct answer choice should be B. Here's how I approached the problem
Total cost = 10 + (n-1)*1 = 9 + n
statement I
total cost > 30 ---> 9 + n > 30 ---> n > 21 well this is insufficient since n could be 22 or 25 cross out A and D
statement II
average = total cost/n = (9 + n)/n = 1.36 since you can calculate the exact value of n this is sufficient to answer the question. If you solve the equation, you get n = 25 sufficient
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RonPurewal
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Post subject: Re: Delivery order of desk chairs...Prep 2 Math Posted: Sat Jan 09, 2010 4:52 am |
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Posts: 7146
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shrads.jp wrote: i want to just correct to wht is written...
It should be 22 chairs,less than 24 : total cost $29.92, less than 30
the other statement is correct
Then the answer can be inferred as B huh? $29.92? the price of the order is $10.00 for the first chair, and $1.00 for each additional chair. how did you get these (whole numbers of dollars) to add up to 29 dollars and 92 cents?
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RonPurewal
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Post subject: Re: Delivery order of desk chairs...Prep 2 Math Posted: Sat Jan 09, 2010 4:52 am |
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Posts: 7146
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mikrodj wrote: I also think the correct answer choice should be B. Here's how I approached the problem
Total cost = 10 + (n-1)*1 = 9 + n
statement I
total cost > 30 ---> 9 + n > 30 ---> n > 21 well this is insufficient since n could be 22 or 25 cross out A and D
statement II
average = total cost/n = (9 + n)/n = 1.36 since you can calculate the exact value of n this is sufficient to answer the question. If you solve the equation, you get n = 25 sufficient yes.
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pratik.munjal
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Post subject: Re: Delivery order of desk chairs...Prep 2 Math Posted: Mon Dec 12, 2011 11:50 am |
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Hmm...one of the questions that uses "fixed cost-variable cost principle". One would be very tempted to choose C after a cursory glance. But a detailed approach points to a different thing.
Let the additional chairs be x (I can see people saying, "Uhh...how original!)
From the question, I form an equation
Total Cost = Fixed Cost + Variable Cost
Total Cost = $10 + (x-1) * $1 (Solve this further- $9 + x )
Statement 1-
Total Cost is more than 30.
9+x>30
x>21. So the question is how much more? 1, 2, 22, or 5 billion. In the absence of a "unique solution", reject the answer choice.
Statement 2-
Now we're talking!
9+x/x=1.36
A value for x can be found. Thus statement 2 is sufficient.
The answer is B
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RonPurewal
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Post subject: Re: Delivery order of desk chairs...Prep 2 Math Posted: Sat Dec 24, 2011 1:01 am |
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Posts: 7146
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pratik.munjal wrote: One would be very tempted to choose C after a cursory glance. But a detailed approach points to a different thing. yes indeed. and this is something that you should always keep in mind on data sufficiency -- anything that you are “tempted to pick after a cursory glance” should be regarded with extreme suspicion. remember that the test is adaptive; if you are scoring high, then you are going to get questions that most people have gotten incorrect. so, put two and two together: if you are looking at a supposedly obvious answer, but most people have missed the problem ... then you know what's going on.
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