Question
In a competitive examination containing 200 questions, 2
marks are awarded for every correct answer and 1 mark gets deducted for every wrong answer. If a student attempted all questions and obtained 97 marks, how many wrong answers must he have given?Solution
Let number of questions with right answers = x ∴ No. of questions with wrong answers = 200 –x ∴ Marks obtained for right answers = 2x ∴ Marks deducted for wrong answers = 200 -x ∴ 2x – (200-x) = 97 ⇒ 3x = 200 + 97 ⇒ 3x = 297 ∴ x= 99 ∴ No. of questions with wrong answers (200 – 99) = 101
Twin prime numbers are the prime numbers whose difference is always equal to 2. The number of twin primes between 35 and 100 is:
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