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M07: Q25 [#permalink]
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25 Aug 2008, 19:36
If 40% of unsuccessful suicide attempts are repeated within 6 months and 25% of suicides are successful, what percentage of suicides in any 6 months period is the first attempt?
30 40 50 60 70
I keep getting 77. Out of 100 initial attempts, 75 un succ. Out of these 75, 40% are attempted again, or 30. Out of the these 30 attempts, 7.5 are successful. When they say suicides, they mean successful ones right? If so, there are 25 + 7.5 total, or 32.5. 25/32.5 = appr 77 %
I think I'm missing something. Can anyone show how to get the OA, 70? Thanks



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Re: M07: Q25 [#permalink]
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26 Aug 2008, 05:43
Aren't 100% of suicides "successful" otherwise they'd be attempted suicides? tamg08 wrote: If 40% of unsuccessful suicide attempts are repeated within 6 months and 25% of suicides are successful, what percentage of suicides in any 6 months period is the first attempt?
30 40 50 60 70
I keep getting 77. Out of 100 initial attempts, 75 un succ. Out of these 75, 40% are attempted again, or 30. Out of the these 30 attempts, 7.5 are successful. When they say suicides, they mean successful ones right? If so, there are 25 + 7.5 total, or 32.5. 25/32.5 = appr 77 %
I think I'm missing something. Can anyone show how to get the OA, 70? Thanks
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Re: M07: Q25 [#permalink]
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26 Aug 2008, 11:41
I would assume so. ha ha. Even if you look at attempts though, it would be still be 77%, 100/130 = apprx .77.



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Re: M07: Q25 [#permalink]
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27 Aug 2008, 12:08
tamg08 wrote: If 40% of unsuccessful suicide attempts are repeated within 6 months and 25% of suicides are successful, what percentage of suicides in any 6 months period is the first attempt?
30 40 50 60 70
I keep getting 77. Out of 100 initial attempts, 75 un succ. Out of these 75, 40% are attempted again, or 30. Out of the these 30 attempts, 7.5 are successful. When they say suicides, they mean successful ones right? If so, there are 25 + 7.5 total, or 32.5. 25/32.5 = appr 77 %
I think I'm missing something. Can anyone show how to get the OA, 70? Thanks Think in this way.. assume 100 sucide attemps.. 25 successful 75 unsuccessfull. 40% of unsuccessful suicide attempts are repeated =40% sucide attempts are second attempt = 30 % first atttempt = 10030 =70%
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Re: M07: Q25 [#permalink]
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27 Jul 2009, 09:23
Quote: Think in this way.. assume 100 sucide attemps.. 25 successful 75 unsuccessfull. 40% of unsuccessful suicide attempts are repeated =40% sucide attempts are second attempt = 30
% first atttempt = 10030 =70%
I don't agree with this method, since it assumes that out of the 25 successful attempts, none of them were reattempts. It only considers the 75% unsuccessful, but for all we know, from the 25 successful attempts, a good portion of them may have been repeats. I agree with the OA and kept getting 77%. 100 people = 100 attempts 25 successful, 75 not 75 not, 40% repeat = 35 repeats 35 repeats, 25% success = 7.5 success so out of the total suicides, 32.5, 25 were first attempts or 77%. Even if we lengthen the time, 100 people = 100 attempts 25 successful, 75 not 75 not, 40% repeat = 35 repeats 35 repeats, 25% success = 7.5 success, 27.5 not 27.5 not, 40% repeat = 11 repeats 11 repeats, 25% success = 2.75 successful so out of the total suicides, 25+7.5+2.75 = 32.5, 32 were first attempts 77% were first attempts, i don't think it would ever converge to 70%. so why isn't the answer 77



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Re: M07: Q25 [#permalink]
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27 Jul 2009, 20:11
bipolarbear wrote: Quote: Think in this way.. assume 100 sucide attemps.. 25 successful 75 unsuccessfull. 40% of unsuccessful suicide attempts are repeated =40% sucide attempts are second attempt = 30
% first atttempt = 10030 =70%
I don't agree with this method, since it assumes that out of the 25 successful attempts, none of them were reattempts. It only considers the 75% unsuccessful, but for all we know, from the 25 successful attempts, a good portion of them may have been repeats. I agree with the OA and kept getting 77%. 100 people = 100 attempts 25 successful, 75 not 75 not, 40% repeat = 35 repeats35 repeats, 25% success = 7.5 success so out of the total suicides, 32.5, 25 were first attempts or 77%. Even if we lengthen the time, 100 people = 100 attempts 25 successful, 75 not 75 not, 40% repeat = 35 repeats 35 repeats, 25% success = 7.5 success, 27.5 not 27.5 not, 40% repeat = 11 repeats 11 repeats, 25% success = 2.75 successful so out of the total suicides, 25+7.5+2.75 = 32.5, 32 were first attempts 77% were first attempts, i don't think it would ever converge to 70%. so why isn't the answer 77 Attempts = 100 Successful = 25 Unsuccessful = 75 Repeat = 40% of unsucessful = .4x75 = 30 New attempt = 100  30 = 70
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Re: M07: Q25 [#permalink]
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27 Jul 2009, 20:20
tamg08 wrote: If 40% of unsuccessful suicide attempts are repeated within 6 months and 25% of suicides are successful, what percentage of suicides in any 6 months period is the first attempt?
30 40 50 60 70
I keep getting 77. Out of 100 initial attempts, 75 un succ. Out of these 75, 40% are attempted again, or 30. Out of the these 30 attempts, 7.5 are successful. When they say suicides, they mean successful ones right? If so, there are 25 + 7.5 total, or 32.5. 25/32.5 = appr 77 %
I think I'm missing something. Can anyone show how to get the OA, 70? Thanks Probably any is not correct here. Any includes the first month in which all (100%) sucides are first attempt.
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Re: M07: Q25 [#permalink]
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30 Sep 2009, 14:40
There is no initial month on this problem. Given that it asks for percentages, the word "any" is not relevant, as the percentage will be the same for any period. The question does not ask "what percentage of attempted suicides in any 6 months period is a first attempt?". It asks "what percentage of suicides in any 6 months period is a first attempt?". Therefore, the official explanation is wrong. Attempts = 100 Successful = 25 Unsuccessful = 75 Repeat = 40% of unsuccessful = .4x75 = 30 Succesful repeats = 25% of 30 = 7.5 1st attempt successful / total suicides = 1st attempt successful / (1st attemp successful + 2nd attempt successful) = 25 / (25 + 7.5) = 77%This question should be revised. Cheers
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Re: M07: Q25 [#permalink]
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11 Jul 2010, 04:09
It should be 77 as explained above. This question really needs revision.
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Re: M07: Q25 [#permalink]
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02 Aug 2010, 06:32
I have some trouble understanding the solution. Please see my reasoning below and advice.
Assume that in each 6 month period the first time attempts are 100. In the first attempt  Attempt  100 Successful  25 Unsuccessful  75
In the second attempt  Attempt = 100 + 30 (40% of Unsuccessful from previous attemp) = 130 Successful  32.5 Unsuccessful  97.5
First time attempts as a percentage = (13030)/130 * 100 = 77%
The OA assumes that 100 attempts in the second attempt include re attempts as well. Is it right?



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Re: M07: Q25 [#permalink]
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02 Jun 2011, 10:17
reminder from latest test taker, please revise the answer to 77%
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