Multiple choice

In the following question, a number series is given with one term missing. Choose the correct alternative which will complete the series. 165, 195, 255, 285, 345, ?

  1. 380

  2. 420

  3. 435

  4. 390

Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Each term is 5 times a prime number. 5 × 11 = 55 (but 11 is prime), 5 × 13 = 65, 5 × 17 = 85, 5 × 19 = 95. However, the sequence shows 165, 195, 255, 285, which are actually 15 × 11, 15 × 13, 15 × 17, 15 × 19. The pattern is 15 × consecutive primes: 11, 13, 17, 19, 23. Next: 15 × 23 = 345. Wait, that's already in the sequence. The actual pattern continues: 15 × 29 = 435.