1,5,6,25,26,30,31,125,126,130,131,150,151,155,156,………What is the value of 30th term in the given series?(a)781(b)3125(c)776(d) 780

• the answer will be 780.
  as we can see the 2,4,6,8,10...positions
  all are multiple of 5 with digits one after and the odd digits are +1 to that
  so the sequence is like 5*5 for the 4th position and +1 to the 5th position
  same manner 6th position 5*6 n 7th is 5*6+1
  8th is multiplying the 2nd n 4th position n 9th is +1 to that
  10th place is multiplying the 2nd n 5th position n 11th is +1 to that
  
  in the same way for 30th position...
  we will multiply 5 with the 15th position i.e. 5*156
• 12 years agoHelpfull: Yes(9) No(2)
• b) 3125
  
  1,5,1+5
  1,5,6,25,25+1,25+5,25+6
  1,5,6,25,26,30,31,125,125+1,125+5,125+6,125+25,125+26,125+30,125+31
  1,5,6..............................................................,625,625+1...
  this will cover 29th term then next will be 3125
• 12 years agoHelpfull: Yes(4) No(1)
• jagjeet u r excellent
• 12 years agoHelpfull: Yes(2) No(0)
• 780..:)
  1 5 6 25 26 30 31 125 126 130 131 150 151 155 156 625 626 630 631 650 651 655 656 750 751 755 756 775 776 780 781.
  
  Logic - Given above by Jagjeet.
• 12 years agoHelpfull: Yes(2) No(1)
• 156*5=780
  
• 12 years agoHelpfull: Yes(2) No(1)
• 1,
  5 =(5*1)=(5*1st term), 6=(5+1) ,
  25=(5*5)=(5*2nd term), 26=(25+1),
  30=(5*6)=(5*3rd term), 31(30+1) ,
  125=(5*25)=(5*4th term), 126=(125+1),
  And so on
  14th term =155=(5*31)
  15th term =155+1 =156
  And 30th term = 5*15th term =5*156=780
  
• 11 years agoHelpfull: Yes(2) No(0)
• answer will be 781.observe the sequence, we find that the numbers in even positions are always odd.so as 30th term is an even position, the answer must be an odd number.so options (c) and (d) are wrong.option (b) is also wrong as it cant be that large.so i think it is option (a)781
• 12 years agoHelpfull: Yes(0) No(7)
• 1,
  5 =(5*1)=(5*1st term), 6=(5+1) ,
  25=(5*5)=(5*2nd term), 26=(25+1),
  30=(5*6)=(5*3rd term), 31(30+1) ,
  125=(5*25)=(5*4th term), 126=(125+1),
  And so on
  14th term =155=(5*31)
  15th term =155+1 =156
  And 30th term = 5*15th term =5*156=780
• 8 years agoHelpfull: Yes(0) No(0)