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During a recent evaluation, X students were given a two-ques

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gmatbull
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During a recent evaluation, X students were given a two-ques [#permalink] New post   Updated on: 02 Feb 2014, 01:45
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During a recent evaluation, X students were given a two-question test. If 1/5 of the students answered the first question correctly, and, of those students, 1/2 answered the second question correctly, which of the following expressions indicates the number of students who did NOT answer both questions correctly?

(A) x/10
(B) x/5
(C) 5x/7
(D) 9x/10
(E) 9x

Show Spoiler
Correct Ans is 9x/10- supported by CASE 2 in attachment

How would the question be asked if it were ONLY the intersection of those who got both questions wrong?
See CASE 1 in attachment

Thanks to respond with any other sample questions
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D

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Originally posted by gmatbull on 01 Feb 2014, 20:52.
Last edited by Bunuel on 02 Feb 2014, 01:45, edited 2 times in total.
Renamed the topic, edited the question and added the OA.
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Re: During a recent evaluation, X students were given a two-ques [#permalink] New post   02 Feb 2014, 01:56
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gmatbull wrote:
During a recent evaluation, X students were given a two-question test. If 1/5 of the students answered the first question correctly, and, of those students, 1/2 answered the second question correctly, which of the following expressions indicates the number of students who did NOT answer both questions correctly?

(A) x/10
(B) x/5
(C) 5x/7
(D) 9x/10
(E) 9x

Show Spoiler
Correct Ans is 9x/10- supported by CASE 2 in attachment

How would the question be asked if it were ONLY the intersection of those who got both questions wrong?
See CASE 1 in attachment

Thanks to respond with any other sample questions


Say x = 10:

The number of students who answered the first question correctly = 10*1/5 = 2;
Of those 2 students, 1/2 answered the second question correctly, thus 2*1/2 = 1 student answered both questions correctly.

If 1 student answered both questions correctly, then the remaining 9 students did NOT answer both questions correctly.

Now, plugging x = 10, and see which of the options gives 9. Only D fits.

Answer: D.

As for your question, for case 1 the question would be "which of the following expressions indicates the number of students who answered both questions WRONG?"

Hope it's clear.
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Re: During a recent evaluation, X students were given a two-ques [#permalink] New post   02 Feb 2014, 06:10
i got it....

Thanks
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Re: During a recent evaluation, X students were given a two-ques [#permalink] New post   29 Mar 2015, 07:58
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gmatbull wrote:
During a recent evaluation, X students were given a two-question test. If 1/5 of the students answered the first question correctly, and, of those students, 1/2 answered the second question correctly, which of the following expressions indicates the number of students who did NOT answer both questions correctly?

(A) x/10
(B) x/5
(C) 5x/7
(D) 9x/10
(E) 9x

Show Spoiler
Correct Ans is 9x/10- supported by CASE 2 in attachment

How would the question be asked if it were ONLY the intersection of those who got both questions wrong?
See CASE 1 in attachment

Thanks to respond with any other sample questions



Let x = 10.

1/5th students answered the first question correctly = 1/5 * 10 = 2.
Of those 2 students, 1/2 answered the second question correctly = 1/2 * 2 = 1.
This is the number of students who answered BOTH questions correctly.

Hence there are 9 students who did NOT answer both questions correctly.
i.e, 9 out of 10 did not answer both questions correctly.
Hence 9x/10.

Hence option (D).

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Re: During a recent evaluation, X students were given a two-ques [#permalink] New post   12 Oct 2020, 04:54
can anyone solve this by Matrix method.
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Re: During a recent evaluation, X students were given a two-ques [#permalink] New post   18 Feb 2022, 10:30
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Re: During a recent evaluation, X students were given a two-ques [#permalink]
18 Feb 2022, 10:30
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