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# Last year Luis invested x dollars for one year, half at 8

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Senior Manager
Joined: 25 Jun 2009
Posts: 302
Last year Luis invested x dollars for one year, half at 8 [#permalink]

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03 Aug 2009, 01:00
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Last year Luis invested x dollars for one year, half at 8 percent simple annual interest and the other half at 12 percent simple annual interest. Now he wants to reinvest the x dollars for one year in the same two types of investments, but the lower rate has decreased. If the higher rate is unchanged, what fraction of the x dollars must he reinvest at the 12 percent rate so that the total interest earned from the x dollars will be the
same for both years ?

(1) The lower rate is now 6 percent.
(2) The total amount of interest earned from the two investments last year was $3,000. [Reveal] Spoiler: OA is A, I think it should be C CEO Joined: 17 Nov 2007 Posts: 3584 Concentration: Entrepreneurship, Other Schools: Chicago (Booth) - Class of 2011 GMAT 1: 750 Q50 V40 Re: I think OA is wrong.. ! need help ! [#permalink] ### Show Tags 03 Aug 2009, 01:11 1 This post received KUDOS Expert's post I think OA is correct. half at 8% and half at 12% means 10% for x. if we have 6% and 12% and still want to get 10% we need (my fast approach): 6 <--4-->10<--2-->12 or 4/(4+2)=2/3 invest at 12%. It is a typical DS C-trap for % and means: often we don't need to know absolute value. So, if you are solving % problem and see absolute value only in options - be careful. _________________ HOT! GMAT TOOLKIT 2 (iOS) / GMAT TOOLKIT (Android) - The OFFICIAL GMAT CLUB PREP APP, a must-have app especially if you aim at 700+ | PrepGame Senior Manager Joined: 25 Jun 2009 Posts: 302 Re: I think OA is wrong.. ! need help ! [#permalink] ### Show Tags 03 Aug 2009, 01:22 walker wrote: I think OA is correct. half at 8% and half at 12% means 10% for x. if we have 6% and 12% and still want to get 10% we need (my fast approach): 6 <--4-->10<--2-->12 or 4/(4+2)=2/3 invest at 12%. It is a typical DS C-trap for % and means: often we don't need to know absolute value. So, if you are solving % problem and see absolute value only in options - be careful. Thanks walker ... ! you made it easier and the fast approach is nice.. ! Senior Manager Joined: 17 Jul 2009 Posts: 286 Concentration: Nonprofit, Strategy GPA: 3.42 WE: Engineering (Computer Hardware) Re: I think OA is wrong.. ! need help ! [#permalink] ### Show Tags 03 Aug 2009, 16:58 statement 1 is sufficient since the question asks for the fraction, not the actual amount...via statement 1, you'll get 1/6...to move over to 12% from 6% Manager Joined: 22 Mar 2008 Posts: 53 Re: I think OA is wrong.. ! need help ! [#permalink] ### Show Tags 05 Aug 2009, 06:52 statement 1 is sufficient. we need only the ratio, not the actual amount. Manager Joined: 18 Jul 2009 Posts: 169 Location: India Schools: South Asian B-schools Re: I think OA is wrong.. ! need help ! [#permalink] ### Show Tags 05 Aug 2009, 08:24 it will be easier to solve it with mixture and alligation approach... given calculate the total rate of interest ...u will see that it is x/10 hence resulting mixture will have 10% rate mixture 1 (x/2 @ 8% ) ---->> ( total interest x @ 10%) <<---- mixture 2 ( x/2 @ 12%) also ratio is given of split of total money x as 1:1 Statement (1) lower rate is 6%, hence a:b can be worked out ; which is nothing but our ans mixture 1 (a @ 6% ) ---->> ( total interest x @ 10%) <<---- mixture 2 ( b @ 12%) Statement (2) The total amount of interest$ 3000 hence total amount is $30,000 (10% interest rate resulted ...refer given) ... mixture 1 (a @ z% ) ---->> ( total interest x @ 10% =$ 3000) <<---- mixture 2 ( b @ 12%)

this only results in (12%-10%) / (10%-z%) = a/b ..... 2/(10-z) = a/b....after using ratio properties also it is insufficient to ans.....

Hence OA A

if u like my post..consider it for kudos
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Bhushan S.
If you like my post....Consider it for Kudos

Re: I think OA is wrong.. ! need help !   [#permalink] 05 Aug 2009, 08:24
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