If 75 % of a class answered the first question on a certain test correctly, 55 percent answered the second question on the test correctly, and 20 percent answered neither of the questions correctly, what percentage answered both correctly?

• 50% answered both correctly.
  
  n(a^b) = n(a)+n(b)-n(a U b)
  = 0.75+0.55-0.8
  = 0.5
  = 0.5*100
  = 50%
• 11 years agoHelpfull: Yes(43) No(0)
• 75% of student gives correct ans for first ques
  55% of student gives correct ans for second quss
  20% of student gives neither ,means 80% gives either of ques
  hence.
  n(A∩B)=n(A)+n(B)-n(AUB)
  =75+55-80
  =50%
• 11 years agoHelpfull: Yes(22) No(1)
• IF 75 PERCNT GIVE CORRECT ANS FOR Q1
  55 PERCNT GIVE CORRECT ANS FOR Q2
  AND 20 PERCNT GIVE NEITHER CORRECT ANS FOR ANY QUES
  IT MEANS 80 PERCNT GIVE ONLY 1 CORRECT ANS IT MAY BE Q1 OR Q2
  SO ADD 75+55=130 AND IT SUBTRACT FROM 80.THAT MEANS 130-80=50% ANS
• 10 years agoHelpfull: Yes(6) No(0)
• 50 % of the people answer both the questions correctly
  75+55 = 130
  100-20 = 80
  130-80 = 50
  so 50/100*100 = 50 % is the correct answer
  
• 9 years agoHelpfull: Yes(3) No(0)
• probabilty of both question to be answered correctly=75/100*55/100
  =41.3%
• 11 years agoHelpfull: Yes(2) No(21)
• let strength of class = 100
  no. of students with no correct ans= 20
  no. of students with correct ans= 80
  1 ques correctly answered by = 75 students(80-75=5 students left ) these 5 would have answered only 2nd question correctly out of 55 who answered 2nd ques correctly
  so no. of students withs both ques correctly answered = 55-5 = 50 i.e 50%
• 9 years agoHelpfull: Yes(1) No(0)
• 20% answered neither of the questions correctly then 80% is currect
  80=75+55-(aꓵb)
  80=130-(aꓵb)
  (aꓵb)=130-80
  (aꓵb)=50
• 7 years agoHelpfull: Yes(0) No(0)