Need clarification in finding the probability of the problem.












0












$begingroup$


In an exam , students were sitting for theoretical and practical test.It is found that no students failed in both subject.$85$% passed in theoretical and $70$% passed in practical test. Calculate probability for a randomly chosen student



(1)failed in both test.



(2)passed in both test.



(3)passed in theoretical test,it is confirmed that the student passed in practical test.



SOLVED






probability







share|cite|improve this question











$endgroup$












  • $begingroup$
    You should only ask one thing per question.
    $endgroup$
    – Ross Millikan
    Dec 16 '18 at 16:17










  • $begingroup$
    yes, I actually want the answer of "b",and wanna check if "a" is correct or not.
    $endgroup$
    – Rakibul Islam Prince
    Dec 16 '18 at 16:19










  • $begingroup$
    I have done a, please delete b and ask it separately.
    $endgroup$
    – Ross Millikan
    Dec 16 '18 at 16:20










  • $begingroup$
    @RakibulIslamPrince I´ve deleted my answer since the answer of Ross was sufficient for your.
    $endgroup$
    – callculus
    Dec 16 '18 at 16:39


















0












$begingroup$


In an exam , students were sitting for theoretical and practical test.It is found that no students failed in both subject.$85$% passed in theoretical and $70$% passed in practical test. Calculate probability for a randomly chosen student



(1)failed in both test.



(2)passed in both test.



(3)passed in theoretical test,it is confirmed that the student passed in practical test.



SOLVED






probability







share|cite|improve this question











$endgroup$












  • $begingroup$
    You should only ask one thing per question.
    $endgroup$
    – Ross Millikan
    Dec 16 '18 at 16:17










  • $begingroup$
    yes, I actually want the answer of "b",and wanna check if "a" is correct or not.
    $endgroup$
    – Rakibul Islam Prince
    Dec 16 '18 at 16:19










  • $begingroup$
    I have done a, please delete b and ask it separately.
    $endgroup$
    – Ross Millikan
    Dec 16 '18 at 16:20










  • $begingroup$
    @RakibulIslamPrince I´ve deleted my answer since the answer of Ross was sufficient for your.
    $endgroup$
    – callculus
    Dec 16 '18 at 16:39
















0












0








0





$begingroup$


In an exam , students were sitting for theoretical and practical test.It is found that no students failed in both subject.$85$% passed in theoretical and $70$% passed in practical test. Calculate probability for a randomly chosen student



(1)failed in both test.



(2)passed in both test.



(3)passed in theoretical test,it is confirmed that the student passed in practical test.



SOLVED






probability







share|cite|improve this question











$endgroup$




In an exam , students were sitting for theoretical and practical test.It is found that no students failed in both subject.$85$% passed in theoretical and $70$% passed in practical test. Calculate probability for a randomly chosen student



(1)failed in both test.



(2)passed in both test.



(3)passed in theoretical test,it is confirmed that the student passed in practical test.



SOLVED






probability




probability






share|cite|improve this question















share|cite|improve this question













share|cite|improve this question




share|cite|improve this question








edited Dec 16 '18 at 16:40







Rakibul Islam Prince

















asked Dec 16 '18 at 16:12









Rakibul Islam PrinceRakibul Islam Prince

988211




988211












  • $begingroup$
    You should only ask one thing per question.
    $endgroup$
    – Ross Millikan
    Dec 16 '18 at 16:17










  • $begingroup$
    yes, I actually want the answer of "b",and wanna check if "a" is correct or not.
    $endgroup$
    – Rakibul Islam Prince
    Dec 16 '18 at 16:19










  • $begingroup$
    I have done a, please delete b and ask it separately.
    $endgroup$
    – Ross Millikan
    Dec 16 '18 at 16:20










  • $begingroup$
    @RakibulIslamPrince I´ve deleted my answer since the answer of Ross was sufficient for your.
    $endgroup$
    – callculus
    Dec 16 '18 at 16:39




















  • $begingroup$
    You should only ask one thing per question.
    $endgroup$
    – Ross Millikan
    Dec 16 '18 at 16:17










  • $begingroup$
    yes, I actually want the answer of "b",and wanna check if "a" is correct or not.
    $endgroup$
    – Rakibul Islam Prince
    Dec 16 '18 at 16:19










  • $begingroup$
    I have done a, please delete b and ask it separately.
    $endgroup$
    – Ross Millikan
    Dec 16 '18 at 16:20










  • $begingroup$
    @RakibulIslamPrince I´ve deleted my answer since the answer of Ross was sufficient for your.
    $endgroup$
    – callculus
    Dec 16 '18 at 16:39


















$begingroup$
You should only ask one thing per question.
$endgroup$
– Ross Millikan
Dec 16 '18 at 16:17




$begingroup$
You should only ask one thing per question.
$endgroup$
– Ross Millikan
Dec 16 '18 at 16:17












$begingroup$
yes, I actually want the answer of "b",and wanna check if "a" is correct or not.
$endgroup$
– Rakibul Islam Prince
Dec 16 '18 at 16:19




$begingroup$
yes, I actually want the answer of "b",and wanna check if "a" is correct or not.
$endgroup$
– Rakibul Islam Prince
Dec 16 '18 at 16:19












$begingroup$
I have done a, please delete b and ask it separately.
$endgroup$
– Ross Millikan
Dec 16 '18 at 16:20




$begingroup$
I have done a, please delete b and ask it separately.
$endgroup$
– Ross Millikan
Dec 16 '18 at 16:20












$begingroup$
@RakibulIslamPrince I´ve deleted my answer since the answer of Ross was sufficient for your.
$endgroup$
– callculus
Dec 16 '18 at 16:39






$begingroup$
@RakibulIslamPrince I´ve deleted my answer since the answer of Ross was sufficient for your.
$endgroup$
– callculus
Dec 16 '18 at 16:39












1 Answer
1






active

oldest

votes


















2












$begingroup$

For a2, there are $15%$ that failed theoretical and $30%$ that failed practical. As these sets are disjoint, there were $45%$ that failed one test. For a3 there were $70%$ that passed practical and $55%$ that passed both, so it is $frac {55}{70}$






share|cite|improve this answer









$endgroup$













  • $begingroup$
    I had considered $100$ students.among them $85$ students passed in theoretical and $70$ students passed in practical. then isn't the number of students passed in both test $=85+70-100=60$ according to the formula?then , the probability shouldn't be $60/100=3/5$? where is my mistake?
    $endgroup$
    – Rakibul Islam Prince
    Dec 16 '18 at 16:26












  • $begingroup$
    But $85+70-100=55$
    $endgroup$
    – Ross Millikan
    Dec 16 '18 at 16:33










  • $begingroup$
    oh!!god !!...nothing to say !! thanks for finding the mistake....
    $endgroup$
    – Rakibul Islam Prince
    Dec 16 '18 at 16:35











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1 Answer
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active

oldest

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1 Answer
1






active

oldest

votes









active

oldest

votes






active

oldest

votes









2












$begingroup$

For a2, there are $15%$ that failed theoretical and $30%$ that failed practical. As these sets are disjoint, there were $45%$ that failed one test. For a3 there were $70%$ that passed practical and $55%$ that passed both, so it is $frac {55}{70}$






share|cite|improve this answer









$endgroup$













  • $begingroup$
    I had considered $100$ students.among them $85$ students passed in theoretical and $70$ students passed in practical. then isn't the number of students passed in both test $=85+70-100=60$ according to the formula?then , the probability shouldn't be $60/100=3/5$? where is my mistake?
    $endgroup$
    – Rakibul Islam Prince
    Dec 16 '18 at 16:26












  • $begingroup$
    But $85+70-100=55$
    $endgroup$
    – Ross Millikan
    Dec 16 '18 at 16:33










  • $begingroup$
    oh!!god !!...nothing to say !! thanks for finding the mistake....
    $endgroup$
    – Rakibul Islam Prince
    Dec 16 '18 at 16:35
















2












$begingroup$

For a2, there are $15%$ that failed theoretical and $30%$ that failed practical. As these sets are disjoint, there were $45%$ that failed one test. For a3 there were $70%$ that passed practical and $55%$ that passed both, so it is $frac {55}{70}$






share|cite|improve this answer









$endgroup$













  • $begingroup$
    I had considered $100$ students.among them $85$ students passed in theoretical and $70$ students passed in practical. then isn't the number of students passed in both test $=85+70-100=60$ according to the formula?then , the probability shouldn't be $60/100=3/5$? where is my mistake?
    $endgroup$
    – Rakibul Islam Prince
    Dec 16 '18 at 16:26












  • $begingroup$
    But $85+70-100=55$
    $endgroup$
    – Ross Millikan
    Dec 16 '18 at 16:33










  • $begingroup$
    oh!!god !!...nothing to say !! thanks for finding the mistake....
    $endgroup$
    – Rakibul Islam Prince
    Dec 16 '18 at 16:35














2












2








2





$begingroup$

For a2, there are $15%$ that failed theoretical and $30%$ that failed practical. As these sets are disjoint, there were $45%$ that failed one test. For a3 there were $70%$ that passed practical and $55%$ that passed both, so it is $frac {55}{70}$






share|cite|improve this answer









$endgroup$



For a2, there are $15%$ that failed theoretical and $30%$ that failed practical. As these sets are disjoint, there were $45%$ that failed one test. For a3 there were $70%$ that passed practical and $55%$ that passed both, so it is $frac {55}{70}$







share|cite|improve this answer












share|cite|improve this answer



share|cite|improve this answer










answered Dec 16 '18 at 16:19









Ross MillikanRoss Millikan

299k24200374




299k24200374












  • $begingroup$
    I had considered $100$ students.among them $85$ students passed in theoretical and $70$ students passed in practical. then isn't the number of students passed in both test $=85+70-100=60$ according to the formula?then , the probability shouldn't be $60/100=3/5$? where is my mistake?
    $endgroup$
    – Rakibul Islam Prince
    Dec 16 '18 at 16:26












  • $begingroup$
    But $85+70-100=55$
    $endgroup$
    – Ross Millikan
    Dec 16 '18 at 16:33










  • $begingroup$
    oh!!god !!...nothing to say !! thanks for finding the mistake....
    $endgroup$
    – Rakibul Islam Prince
    Dec 16 '18 at 16:35


















  • $begingroup$
    I had considered $100$ students.among them $85$ students passed in theoretical and $70$ students passed in practical. then isn't the number of students passed in both test $=85+70-100=60$ according to the formula?then , the probability shouldn't be $60/100=3/5$? where is my mistake?
    $endgroup$
    – Rakibul Islam Prince
    Dec 16 '18 at 16:26












  • $begingroup$
    But $85+70-100=55$
    $endgroup$
    – Ross Millikan
    Dec 16 '18 at 16:33










  • $begingroup$
    oh!!god !!...nothing to say !! thanks for finding the mistake....
    $endgroup$
    – Rakibul Islam Prince
    Dec 16 '18 at 16:35
















$begingroup$
I had considered $100$ students.among them $85$ students passed in theoretical and $70$ students passed in practical. then isn't the number of students passed in both test $=85+70-100=60$ according to the formula?then , the probability shouldn't be $60/100=3/5$? where is my mistake?
$endgroup$
– Rakibul Islam Prince
Dec 16 '18 at 16:26






$begingroup$
I had considered $100$ students.among them $85$ students passed in theoretical and $70$ students passed in practical. then isn't the number of students passed in both test $=85+70-100=60$ according to the formula?then , the probability shouldn't be $60/100=3/5$? where is my mistake?
$endgroup$
– Rakibul Islam Prince
Dec 16 '18 at 16:26














$begingroup$
But $85+70-100=55$
$endgroup$
– Ross Millikan
Dec 16 '18 at 16:33




$begingroup$
But $85+70-100=55$
$endgroup$
– Ross Millikan
Dec 16 '18 at 16:33












$begingroup$
oh!!god !!...nothing to say !! thanks for finding the mistake....
$endgroup$
– Rakibul Islam Prince
Dec 16 '18 at 16:35




$begingroup$
oh!!god !!...nothing to say !! thanks for finding the mistake....
$endgroup$
– Rakibul Islam Prince
Dec 16 '18 at 16:35


















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