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20 students take a test with three questions A,B and C. 16 students answer at least one question correctly. 10 answer question A correctly, 8 answer question B correctly, 6 answer question C correctly. 3 students answer both A and B correctly, 4 answer A and C correctly and 1 student answers all three questions correctly. How many students answer questions B and C correctly?

What would be the approach to solving this problem? I am aware the answer is 2 but would like understand concepts more. Thanks

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    $\begingroup$ Have a look at Venn diagrams: en.wikipedia.org/wiki/Venn_diagram $\endgroup$ – jvdhooft Jun 2 '17 at 12:16
  • $\begingroup$ ok thanks i was able to draw the venn diagram $\endgroup$ – user2287434 Jun 2 '17 at 12:22
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    $\begingroup$ Are you familiar with Inclusion-Exclusion principle? $\endgroup$ – Prajwal Kansakar Jun 2 '17 at 12:36
  • $\begingroup$ No but I will research it, thanks $\endgroup$ – user2287434 Jun 2 '17 at 12:49
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Try to understand the venn diagram and the Inclusion-Exclusion principle. Both are the concept to solve the problem above.

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