If the closing price of stock X on the first trading day last year

Question

If the closing price of stock X on the first trading day last year was $10, was the closing price of stock X at least $5 on each of the trading days last year?

(1) Last year, the highest closing price of stock X was twice the lowest closing price of stock X.

(2) The highest closing price of stock X last year was $16.

Bunuel · Accepted Answer

If the closing price of stock X on the first trading day last year was $10, was the closing price of stock X at least $5 on each of the trading days last year?

(1) Last year, the highest closing price of stock X was twice the lowest closing price of stock X.

Given that on one of the days the price was $10, this implies that the highest price cannot be less than that, therefore, the lowest price of the stock could not possibly be less than $10/2 = $5. Sufficient.

(2) The highest closing price of stock X last year was $16.

The above is clearly insufficient. All we know is that the highest price of the stock was $16 and on the first day, the price was $10. On all other days, the prices of the stocks could have been anywhere from 0 to 16. Not sufficient.

Answer A.

gmatophobia · Answer

Statement 1

(1) Last year, the highest closing price of stock X was twice the lowest closing price of stock X.

We know that the trading price of the stock on at least one of the days was $10. Let's assume that this was the highest price of the stock. The lowest price of the stock therefore was $5.

Was the closing price of stock X at least $5 on each of the trading days last year → The answer to this question is Yes.

The statement alone is sufficient. We can eliminate B, C, and E.

Statement 2

(2) The highest closing price of stock X last year was $16.

We do not have any information on the lowest value. If the lowest value of the stock on each of the trading days last year was at least $5, the answer to the target question will be Yes. On the contrary, if the lowest value of the stock on at least one of the trading days last year was less than $5, the answer to the target question is No.

As we are getting two contradicting answers, the statement alone is not sufficient.

Option A

sachi-in · Answer

Question seems exactly the type GMAT would love in the DI section:

Just careful reading and then thinking of the situation would reveal the following:

1st day price = 10, It means highest closing price >= 10.

People are likely to choose the wrong option C i.e both info is required if they overlook the trick GMAT loves to play with words.

Hence only knowing highest closing price ( >= 10) = 2 * ( lowest closing is enough )

samarpan.g28 · Answer

I thought of the solution in the following ways.

1. Given, the first-day closing price is $10. It is the  highest  for day 1. Considering this, the  lowest  is $10/2=$5 as per the first statement.
2. Given, that the highest closing price in that year was $16. So the lowest will be $16/2=$8. Let me keep this on hold for now.
3. The main statement asks whether the closing price was  ATLEAST  $5 every day. I am not assuming whether the closing price dropped in the subsequent days. What if the closing price went above $10? In that case,  the minimum value has to be $5 mentioned in statement 1.  Therefore I think it is A. That is why I did not bother about statement 2 because even if the closing price is increasing, the minimum is going to be $5 only.

Kindly let me know if my reasoning is correct.

Nsp10 · Answer

Hello  Bunuel  ,  
 if we assume the lowest price to be 10$ and in that case the highest price is 20$ of the stock, so the price is automatically more than 5$ on each of the trading days.
 
 am I thinking right {or missing something as just got little confused as you took only the highest price condition}

Bunuel · Answer

We are asked to find out whether the price of stock X was at least $5 on each of the trading days last year. So, we need to focus on the lowest possible price.

Since on one day the price was $10, the highest price cannot possibly be lower than $10. Even if $10 was the highest, then the lowest must be at least 10/2 = 5. So the price was never below $5.

Nsp10 · Answer

"Thank you for the reply,  Bunuel 
 I completely understand the explanation.
 I was just wondering — if we had assumed $10 to be the lowest price (just in case), then the highest price would have been $20. In that case, the closing price would still be more than $5, right?"

anushree01 · Answer

C trap question.
Key here was understanding at least 5 --> 5 & anything above it

nequep · Answer

what are the five options, I can't see them

Bunuel · Answer

This is a data sufficiency question. Options for DS questions are always the same and usually omitted on the site.

The data sufficiency problem consists of a question and two statements, labeled (1) and (2), in which certain data are given. You have to decide whether the data given in the statements are sufficient for answering the question. Using the data given in the statements, plus your knowledge of mathematics and everyday facts (such as the number of days in July or the meaning of the word counterclockwise), you must indicate whether—

A. Statement (1) ALONE is sufficient, but statement (2) alone is not sufficient to answer the question asked.
B. Statement (2) ALONE is sufficient, but statement (1) alone is not sufficient to answer the question asked.
C. BOTH statements (1) and (2) TOGETHER are sufficient to answer the question asked, but NEITHER statement ALONE is sufficient to answer the question asked.
D. EACH statement ALONE is sufficient to answer the question asked.
E. Statements (1) and (2) TOGETHER are NOT sufficient to answer the question asked, and additional data specific to the problem are needed.

If the closing price of stock X on the first trading day last year

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GMAT Data Sufficiency (DS) Questions

If the closing price of stock X on the first trading day last year

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