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# A telecommunications company’s stock fell 10% last month, while a riva

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Manager
Joined: 04 Aug 2013
Posts: 97
Location: India
Schools: McCombs '17
GMAT 1: 670 Q47 V35
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WE: Manufacturing and Production (Pharmaceuticals and Biotech)
A telecommunications company’s stock fell 10% last month, while a riva  [#permalink]

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26 Nov 2014, 08:32
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Difficulty:

55% (hard)

Question Stats:

62% (02:01) correct 38% (02:07) wrong based on 155 sessions

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A telecommunications company’s stock fell 10% last month, while a rival company’s stock increased by 10%. The rival company’s stock value today is what percentage of the telecommunication company’s stock value at the beginning of last month?

(1) The rival company’s stock was valued at $42 per share at the beginning of last month. (2) The dollar amount of the rival company’s stock increase was 90% as much as the dollar amount of the decrease in the telecommunication company’s stock. Senior Manager Joined: 13 Jun 2013 Posts: 276 A telecommunications company’s stock fell 10% last month, while a riva [#permalink] ### Show Tags 26 Nov 2014, 10:34 1 anceer wrote: A telecommunications company’s stock fell 10% last month, while a rival company’s stock increased by 10%. The rival company’s stock value today is what percentage of the telecommunication company’s stock value at the beginning of last month? (1) The rival company’s stock was valued at$42 per share at the beginning of last month.

(2) The dollar amount of the rival company’s stock increase was 90% as much as the dollar amount of the decrease in the telecommunication company’s stock.

stock price of telecom company at the beginning of the last month = x
stock price of rival telecom company at the beginning of the last month = y
thus stock price of telecom company at the end of the month = .9x and stock price of the rival company at the end of the month = 1.1y

we are required to find out $$\frac{1.1y}{x} * 100$$--------------------1)

st.1 not sufficient as nothing is mentioned about x.

st.2 .1y= .9 (.1x)

y/x= 9/10

substitute the value of y/x in 1) we have, required percentage as 99%

hence statement b alone is sufficient to answer the question.
Manager
Joined: 30 Mar 2013
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Re: A telecommunications company’s stock fell 10% last month, while a riva  [#permalink]

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26 Nov 2014, 13:34
manpreetsingh86 wrote:
anceer wrote:
A telecommunications company’s stock fell 10% last month, while a rival company’s stock increased by 10%. The rival company’s stock value today is what percentage of the telecommunication company’s stock value at the beginning of last month?

(1) The rival company’s stock was valued at $42 per share at the beginning of last month. (2) The dollar amount of the rival company’s stock increase was 90% as much as the dollar amount of the decrease in the telecommunication company’s stock. stock price of telecom company at the beginning of the last month = x stock price of rival telecom company at the beginning of the last month = y thus stock price of telecom company at the end of the month = .9x and stock price of the rival company at the end of the month = 1.1y we are required to find out $$\frac{1.1y}{x} * 100$$--------------------1) st.1 not sufficient as nothing is mentioned about y. st.2 .1y= .9 (.1x) y/x= 9/10 substitute the value of y/x in 1) we have, required percentage as 99% hence statement b alone is sufficient to answer the question. you mean nothing is mentioned about x? Manhattan Prep Instructor Joined: 22 Mar 2011 Posts: 1319 Re: A telecommunications company’s stock fell 10% last month, while a riva [#permalink] ### Show Tags 27 Nov 2014, 00:50 1 An easy way to think about s2 is that it relates the increase in one stock with the decrease in the other. Since both changes are 10% of the original, we can also say it relates the actual values. If we know the ratio of the two original values, we can find the requested ratio if we want to. But this is DS, so we don't want to. _________________ Dmitry Farber | Manhattan GMAT Instructor | New York Manhattan GMAT Discount | Manhattan GMAT Course Reviews | View Instructor Profile | Manhattan GMAT Reviews Senior Manager Joined: 13 Jun 2013 Posts: 276 Re: A telecommunications company’s stock fell 10% last month, while a riva [#permalink] ### Show Tags 27 Nov 2014, 01:09 usre123 wrote: you mean nothing is mentioned about x? yes, it was a typo. thanks for pointing that out. Senior SC Moderator Joined: 14 Nov 2016 Posts: 1314 Location: Malaysia Re: A telecommunications company’s stock fell 10% last month, while a riva [#permalink] ### Show Tags 09 Mar 2017, 00:55 anceer wrote: A telecommunications company’s stock fell 10% last month, while a rival company’s stock increased by 10%. The rival company’s stock value today is what percentage of the telecommunication company’s stock value at the beginning of last month? (1) The rival company’s stock was valued at$42 per share at the beginning of last month.

(2) The dollar amount of the rival company’s stock increase was 90% as much as the dollar amount of the decrease in the telecommunication company’s stock.

Official solution from Veritas Prep.

The correct response is (B). To find the answer we have to know the telecommunication’s stock value last month)/(the rival company’s stock value today) = (.90)(telecomm)/(rival company) = .9(Telecomm/Rival). Statement (1) is insufficient, because it doesn’t tell us the value of the telecommunications company’s stock. Statement (2) may not give us the two values we need, but it does give us their ratio: (0.1)(rival company) = (0.9)(0.1)(telecomm). Sufficient.
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A telecommunications company’s stock fell 10% last month, while a riva  [#permalink]

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09 Mar 2017, 01:09
anceer wrote:
A telecommunications company’s stock fell 10% last month, while a rival company’s stock increased by 10%. The rival company’s stock value today is what percentage of the telecommunication company’s stock value at the beginning of last month?

(1) The rival company’s stock was valued at $42 per share at the beginning of last month. (2) The dollar amount of the rival company’s stock increase was 90% as much as the dollar amount of the decrease in the telecommunication company’s stock. Dear AnthonyRitz & ByjusClasses, Could you help to explain this problem? I am stumped by this question and cannot visualized. _________________ "Be challenged at EVERY MOMENT." “Strength doesn’t come from what you can do. It comes from overcoming the things you once thought you couldn’t.” "Each stage of the journey is crucial to attaining new heights of knowledge." Rules for posting in verbal forum | Please DO NOT post short answer in your post! Advanced Search : https://gmatclub.com/forum/advanced-search/ Senior Manager Status: Come! Fall in Love with Learning! Joined: 05 Jan 2017 Posts: 471 Location: India A telecommunications company’s stock fell 10% last month, while a riva [#permalink] ### Show Tags 09 Mar 2017, 01:56 1 ziyuen Prompt analysis let the stock price of telecommunication company be x and rival's be y at the beginning of month at the and of the month, telecommunication company's price decreases by 10% or 0.1x and rivals increased by 10% i.e. 0.1y, hence at the end of this month their prices will be 0.9x and 1.1y respectively Translation In order to find the percentage for the expression (1.1y/x) x 100, we need: 1# exact value of x and y 2# relation between x and y 3# two variable, two equations. Statement analysis St 1: y = 24, no value of x has been given. INSUFFICIENT. Hence option a and d excluded. St 2: it is given that dollar amount increase in rival's sock = (90/100) x amount decrease in telecommunication stock or 0.1y = 0.9 * 0.1x or y/x = 0.9 putting this value in the expression (1.1y/x) x 100 we get 1.1*0.9*100 = 99%. ANSWER. hence option c and e also excluded Option B I hope this clarify your doubt regarding the question. Hit kudos and visit our page for free GMAT prep articles : http://www.byjus.com/free-gmat-prep _________________ GMAT Mentors Target Test Prep Representative Status: Founder & CEO Affiliations: Target Test Prep Joined: 14 Oct 2015 Posts: 3894 Location: United States (CA) Re: A telecommunications company’s stock fell 10% last month, while a riva [#permalink] ### Show Tags 15 Mar 2017, 16:27 anceer wrote: A telecommunications company’s stock fell 10% last month, while a rival company’s stock increased by 10%. The rival company’s stock value today is what percentage of the telecommunication company’s stock value at the beginning of last month? (1) The rival company’s stock was valued at$42 per share at the beginning of last month.

(2) The dollar amount of the rival company’s stock increase was 90% as much as the dollar amount of the decrease in the telecommunication company’s stock.

If we let the stock value of the rival company at the beginning of last month = x, and the stock value of the telecommunications company at the beginning of last month = y, then we can represent the current value of the rival company’s stock as 1.1x (i.e., with an increase of 0.1x in value) and the current value of the telecommunications company’s stock as 0.9y (with a decrease of 0.1y in value).

We need to determine what percentage the rival company's stock value today is of the telecommunications company’s stock value at the beginning of last month. That is:

(1.1x)/y = ?

Statement One Alone:

The rival company’s stock was valued at \$42 per share at the beginning of last month.

We know that x = 42; however, without knowing any information regarding the other company, we cannot answer the question. Statement one alone is not sufficient.

Statement Two Alone:

The dollar amount of the rival company’s stock increase was 90% as much as the dollar amount of the decrease in the telecommunication company’s stock.

Using the information in statement two, we can create the following equation:

0.1x = 0.9(0.1y)

x = 0.9y

x/y = 0.9

Since we have a value for x/y, statement two alone is sufficient.

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Re: A telecommunications company’s stock fell 10% last month, while a riva &nbs [#permalink] 15 Mar 2017, 16:27
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