Friday, April 10, 2009

GRE DOUBT OF THE DAY

One alloy of metal contains 90%copper & 10%tin. Another alloy contains 95%copper &5%tin. If they are mixed so that the mixture contains 9%tin then what % of copper will it contain?
A)90
B)65
C)85
D)75
E)80

correct answer:75

should'nt it be 100-9=91%?
please explain!!

Sent by: KRITI AGARWAL
at

18 comments:

  1. AnonymousApril 10, 2009 at 11:41 PM

    correct ans 75

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  2. ashwinApril 11, 2009 at 12:01 AM

    it s 91% rite??
    how come 75??

    ReplyDelete
  3. AnonymousApril 11, 2009 at 1:03 AM

    how cum 75??? giv it solution....
    logically it shud b 91 only..

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  4. rohitApril 11, 2009 at 1:06 AM

    it is 91....mathematically it cums out 91 too... logically also... 75 is wrong for sure..

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  5. AnonymousApril 11, 2009 at 12:28 PM

    ok...correct answer is 75 but i also think it is 91%...maybe prinitng error then..thanks guys nonetheless:)

    ReplyDelete
  6. AnonymousApril 11, 2009 at 12:29 PM

    ok...correct answer is 75 but i also think it is 91%...maybe prinitng error then..thanks guys nonetheless:)

    ReplyDelete
  7. AnonymousApril 13, 2009 at 12:01 AM

    TRY THE BOOK TO ERADICATE ALL MATHS QUALMS
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    ReplyDelete
  8. AnonymousApril 16, 2009 at 1:15 PM

    Ans is 75 :
    Solution:
    (90)(10) + (95)(5) = (x)(9)
    x=153

    153 is 75% of 200 ( As we are mixing 2 Alloys i.e (100 +100 )

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  9. AnonymousApril 18, 2009 at 10:17 PM

    pls explain the soln.

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  10. rohitApril 20, 2009 at 10:46 AM

    dere is no logic behind ur solution....its wrong

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  11. UnknownApril 21, 2009 at 3:22 PM

    plz explain clearly

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  12. SwapnilMay 3, 2009 at 2:40 PM

    wat the heck...ur solution is amazingly wrong..u r multiplying Cu and Tin %ages..and equating..absolutly wrong..ans is 91%..bcoz thr is no impurity in either alloys(simple logic)..

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  13. chintuMay 28, 2009 at 8:42 AM

    ur genius with ur innosence?????????is it 75????really

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  14. **July 22, 2009 at 9:10 AM

    if we go with the answer it said
    Cu=75%
    Sn=9%
    total=84%
    where is the rest 16%...
    can anybody explain....as it is mentioned that it contain 2 metals...

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  15. AnonymousAugust 3, 2009 at 1:02 AM

    75

    ReplyDelete
  16. Pankaj AgarwalSeptember 9, 2009 at 3:32 AM

    Answer is 91 % for sure even den
    suppose x : 1 is the proportion in which we mixed it den

    (10 * x + 5)/(x + 1) = 9

    => x = 4/1

    => first mixture : second mixture :: 4 : 1

    => (90 * 4 + 95 * 1)/( 4 + 1) = 91

    so 91 % is correct answer..

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  17. AnonymousAugust 2, 2010 at 11:13 AM

    it´s 65%!

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  18. AnonymousJanuary 7, 2011 at 9:13 AM

    plz explain it

    ReplyDelete