Stocks & Bonds DS question

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rosh26: Master | Next Rank: 500 Posts; Posts: 215; Joined: Mon Apr 21, 2008 8:07 am

by rosh26 » Sat Jun 14, 2008 5:39 pm

Over a certain time period, did the # of stocks in Ruth's portfolio increase?

I Over time period, ratio of the number of shares of stock to the total number of shares of stocks and bonds increased.

II Over time period, total # of shares of stocks and bonds increased

Answer is C - both together

Can someone please explain ?

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Source: Beat The GMAT — Data Sufficiency | Sat Jun 14, 2008 5:39 pm

altin: Junior | Next Rank: 30 Posts; Posts: 10; Joined: Sat Jun 14, 2008 8:45 pm

Re: Stocks & Bonds DS question

by altin » Sat Jun 14, 2008 9:50 pm

(1) let say you have 2 stock and 3 bond
if ratio 2:3 increases that can have 2 meaning
s increased s=3 b=3 ratio 3:3
b decreased s=2 b=2 ratio 2:2 either case ratio increases with 2 different answer
(2) it says both number increased so we can eliminate second part where bond decreased. If we use it together# of stocks increased
answer C

rosh26 wrote:Over a certain time period, did the # of stocks in Ruth's portfolio increase?

I Over time period, ratio of the number of shares of stock to the total number of shares of stocks and bonds increased.

II Over time period, total # of shares of stocks and bonds increased

Answer is C - both together

Can someone please explain ?

Like this post

ildude02: Master | Next Rank: 500 Posts; Posts: 320; Joined: Sun Jan 13, 2008 10:00 pm; Thanked: 10 times

Re: Stocks & Bonds DS question

by ildude02 » Sun Jun 15, 2008 3:21 pm

altin wrote:(1) let say you have 2 stock and 3 bond
if ratio 2:3 increases that can have 2 meaning
s increased s=3 b=3 ratio 3:3
b decreased s=2 b=2 ratio 2:2 either case ratio increases with 2 different answer
(2) it says both number increased so we can eliminate second part where bond decreased. If we use it together# of stocks increased
answer C

rosh26 wrote:Over a certain time period, did the # of stocks in Ruth's portfolio increase?

I Over time period, ratio of the number of shares of stock to the total number of shares of stocks and bonds increased.

II Over time period, total # of shares of stocks and bonds increased

Answer is C - both together

I'm not sure if I understod why (i) by itself is unsufficient. From (i), the ratio is s/(s+b) instead of s: b as you used for the reasoning. For the ratio s/s+b to increase over time, number of S in the portfolio has to increase. Else, the ratio will no increase. Can someone explain if I'm missing something.

Can someone please explain ?

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ildude02: Master | Next Rank: 500 Posts; Posts: 320; Joined: Sun Jan 13, 2008 10:00 pm; Thanked: 10 times

by ildude02 » Sun Jun 15, 2008 3:23 pm

I'm not sure if I understod why (i) by itself is unsufficient. From (i), the ratio is s/(s+b) instead of s: b as altin used for the reasoning . For the ratio s/s+b to increase over time, number of S in the portfolio has to increase. Else, the ratio will not increase. Can someone explain if I'm missing something.

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altin: Junior | Next Rank: 30 Posts; Posts: 10; Joined: Sat Jun 14, 2008 8:45 pm

by altin » Sun Jun 15, 2008 4:21 pm

A ratio of 2:3 ("two to three") means that the whole is made up of 2 parts of one thing and 3 parts of another
you are doing percentage
Let say you have 10 s and 20 b
ratio is 1/2
you lost som b and now you have 10 s and 10 b
ratio is 1/1 ratio has increased but # stock has not

ildude02 wrote:I'm not sure if I understod why (i) by itself is unsufficient. From (i), the ratio is s/(s+b) instead of s: b as altin used for the reasoning . For the ratio s/s+b to increase over time, number of S in the portfolio has to increase. Else, the ratio will not increase. Can someone explain if I'm missing something.

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ildude02: Master | Next Rank: 500 Posts; Posts: 320; Joined: Sun Jan 13, 2008 10:00 pm; Thanked: 10 times

by ildude02 » Sun Jun 15, 2008 4:34 pm

I'm reading the question as ratio of S parts to the whole(S+B). So for the numbers you suggested for S as 10 and B as 20. The ratio I'm using as per (i) is 10/(10+20), s/WHOLE(s+b) = 1/3. I thought that for this ratio to increase, S(the numerator) has to increase without which the ratio will not increase. But now thinking over it again, the ratio can increase if B decreases and S stays constant and it cna also increase if S increases and B stays constant. So it's INSUFFICIENT.

altin wrote:A ratio of 2:3 ("two to three") means that the whole is made up of 2 parts of one thing and 3 parts of another
you are doing percentage
Let say you have 10 s and 20 b
ratio is 1/2
you lost som b and now you have 10 s and 10 b
ratio is 1/1 ratio has increased but # stock has not

ildude02 wrote:I'm not sure if I understod why (i) by itself is unsufficient. From (i), the ratio is s/(s+b) instead of s: b as altin used for the reasoning . For the ratio s/s+b to increase over time, number of S in the portfolio has to increase. Else, the ratio will not increase. Can someone explain if I'm missing something.

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srisanj4: Junior | Next Rank: 30 Posts; Posts: 21; Joined: Sat Dec 27, 2008 3:38 pm

by srisanj4 » Sun May 31, 2009 7:43 pm

The same logic applies when statement 1 and 2 are combined. Isnt that true?

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brick2009: Master | Next Rank: 500 Posts; Posts: 171; Joined: Mon Jun 01, 2009 8:59 pm; Thanked: 8 times

C

by brick2009 » Tue Jun 02, 2009 6:41 am

1) says S/(S+B) went up....

this is possible:
a.) if S goes up
b.) if B goes down...

So A is insufficient...

2.) S+B went up..
again...this can happen a.) if S stay same and B goes up... (in this is true...the S/(S+B) ratio decreases
b.) is S and B both go up.then ratio increases

B is insufficient

Taking both together...b.) of 2 fits 1) and 2.) ...hence C

as the ratio went up (according to 1) and that is possible only if S+B both change...thus S will have to go UP...

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