Find the first number in the series ---,19,23,29,31

• 17
  coz given series is prime no and the prime no b4 19 is 17.
• 10 years agoHelpfull: Yes(3) No(0)
• ANS. 15
  
  here we can see the difference of alternate numbers.
  there is a difference of "8" in between 23 and 31.
  so we have to subtract "8" from 23 to get the 1st number.
• 10 years agoHelpfull: Yes(0) No(1)