JEE MainMathematicsSets and Relations
An auditorium has seats numbered sequentially from 1 to 300 . Seats whose numbers are multiples of 3 are designated as VIP seats. However, a VIP seat is considered 'defective' and removed if its number shares a common factor strictly greater than 1 with 35 . The sum of the numbers of all valid (non-defective) VIP seats is _____.
Correct answer
10110
Step-by-step solution
Total seats are numbered 1 to 300 . The VIP seats are those whose numbers are multiples of 3 . Let V be the set of VIP seat numbers: V = 3, 6, 9, , 300 A VIP seat is defective if its number n satisfies gcd (n, 35) > 1 . Since 35 = 5 7 , a seat is defective if its number is divisible by 5 or 7 . We need to find the sum of valid VIP seats, which are multiples of 3 but not divisible by 5 or 7 . Using the Principle of Inclusion-Exclusion, the required sum is: S_ valid = S₃ - S₁₅ - S₂₁ + S₁₀₅ Sum of multiples of 3 up to