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# Ms. Morris invested in Fund A and Fund B. The total amount

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Magoosh GMAT Instructor
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Ms. Morris invested in Fund A and Fund B. The total amount [#permalink]  26 Oct 2012, 13:02
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68% (03:30) correct 32% (02:34) wrong based on 103 sessions
Ms. Morris invested in Fund A and Fund B. The total amount she invested, in both funds combined, was $100,000. In one year, Fund A paid 23% and Fund B paid 17%. The interest earned in Fund B was exactly$200 greater than the interest earned in Fund A. How much did Ms. Morris invest in Fund A?
(A) $32,000 (B)$36,000
(C) $40,000 (D)$42,000
(E) $45,000 For this question, one could do an algebraic solution, but would it be faster to backsolve from the answers? I would argue for the latter, though I imagine there will be a difference of opinions on this question. My argument, along with a discussion of backsolving in general and a complete solution to this problem, is here: http://magoosh.com/gmat/2012/gmat-plugg ... -choice-c/ Perhaps other experts would also like to chime in on the issue of when to solve algebraically vs. when to backsolve. Mike [Reveal] Spoiler: OA _________________ Mike McGarry Magoosh Test Prep Last edited by mikemcgarry on 26 Oct 2012, 15:28, edited 1 time in total.  Kaplan Promo Code Knewton GMAT Discount Codes Manhattan GMAT Discount Codes Director Joined: 22 Mar 2011 Posts: 613 WE: Science (Education) Followers: 73 Kudos [?]: 529 [1] , given: 43 Re: backsolving [#permalink] 26 Oct 2012, 14:42 1 This post received KUDOS mikemcgarry wrote: Ms. Morris invested in Fund A and Fund B. The total amount she invested, in both funds combined, was$100,000. In one year, Fund A paid 23% and Fund B paid 17%. The interest earned in Fund B was exactly $200 greater than the interest earned in Fund A. How much did Ms. Morris invest in Fund A? (A)$32,000
(B) $36,000 (C)$40,000
(D) $44,000 (E)$45,000

For this question, one could do an algebraic solution, but would it be faster to backsolve from the answers? I would argue for the latter, though I imagine there will be a difference of opinions on this question.

My argument, along with a discussion of backsolving in general and a complete solution to this problem, is here:
http://magoosh.com/gmat/2012/gmat-plugg ... -choice-c/

Perhaps other experts would also like to chime in on the issue of when to solve algebraically vs. when to backsolve.

Mike

The correct answer should be 42,000, and it is not listed neither above, nor in the question you published on your blog.
It just appears in the solution you posted.
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Magoosh GMAT Instructor
Joined: 28 Dec 2011
Posts: 2142
Followers: 539

Kudos [?]: 2262 [0], given: 31

Re: backsolving [#permalink]  26 Oct 2012, 15:30
Expert's post
EvaJager wrote:
The correct answer should be 42,000, and it is not listed neither above, nor in the question you published on your blog.
It just appears in the solution you posted.

Yes, you're right --- a mistake on my part --- the OA is \$42,000, and I just corrected the question above & the blog. Thank you very much.

Mike
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Mike McGarry
Magoosh Test Prep

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Re: Ms. Morris invested in Fund A and Fund B. The total amount [#permalink]  16 Nov 2012, 12:07
Could someone post the algebraic way please
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Re: Ms. Morris invested in Fund A and Fund B. The total amount [#permalink]  16 Nov 2012, 13:07
chibimoon wrote:
Could someone post the algebraic way please

A+B=100k
0.17B=0.23A+200=> -23A+17B=20000

from first equation 23A+23B=2300K
add above and eq2
40B=2320K
B=58K

A=100k-58k=42k
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Re: Ms. Morris invested in Fund A and Fund B. The total amount [#permalink]  02 Feb 2013, 15:35
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chibimoon wrote:
Could someone post the algebraic way please

A+B=100,000

0.17B=0.23A+200

You now have two equations, so you can either substitute or eliminate. In the explanation above, elimination is used, here I use substitution (elimination is easier in this case)

Take away decimals first: 17B=23A+20,000

Isolate first equation to solve for A (your goal): B=100,000-A

Plug in for B:
17(100,000-A)=23A+20,000
1,700,000-17A=23A+20,000
1,680,000=40A
1,680,000/40=A
A=42,000=Answer Choice D
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Magoosh GMAT Instructor
Joined: 28 Dec 2011
Posts: 2142
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Kudos [?]: 2262 [0], given: 31

Re: Ms. Morris invested in Fund A and Fund B. The total amount [#permalink]  02 May 2013, 10:29
Expert's post
Here's another problem from that same article, one that's even less amenable to algebraic treatment.

If the sequence a(n) is defined as a(n) = n^2 + n + \sqrt{n+3}, then which of the following values of n represents the first terms such that a(n) > 500?
(A) 13
(B) 22
(C) 33
(D) 46
(E) 78

[Reveal] Spoiler:
OA = (B)

A full solution is shown at that that article:
http://magoosh.com/gmat/2012/gmat-plugg ... -choice-c/

Mike
_________________

Mike McGarry
Magoosh Test Prep

Re: Ms. Morris invested in Fund A and Fund B. The total amount   [#permalink] 02 May 2013, 10:29
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# Ms. Morris invested in Fund A and Fund B. The total amount

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