2.3.4.15.12
3.4.5.28.20
4.5.6.45.30
5.6.7.a .42
6.7.8.91.56

• value of a will be 66
  simple soln is that serieis given as
  2.3.4.15.12
  3.4.5.28.20
  4.5.6.45.30
  5.6.7.a .42
  6.7.8.91.56 so check each colounm u will find the increasing diff...in 'a' coloumn the diff is of 4..means 15...then 28 diff is of 13..then next term can b find out by adding 4 in 13..means add 17 to 28 u get 45 then same way keep on...
• 13 years agoHelpfull: Yes(8) No(2)
• 2 3 4 5*3 3*4
  3 4 5 7*4 4*5
  4 5 6 9*5 5*6
  5 6 7 11*6 6*7
  6 7 8 13*7 7*8
  So the ans is 66
• 13 years agoHelpfull: Yes(7) No(2)
• 2(first term)+3(thrid term) =5
  5-1= 4
  4 * 3(2nd term) =12 (fourth term)
  proceeding like this...
  5+7 =12
  12-1=11.
  11*6=66
  so a = 66
• 13 years agoHelpfull: Yes(3) No(3)
• 77. 3*5=15
  4*7=28
  5*9=45
  6*11=77
• 13 years agoHelpfull: Yes(2) No(5)
• 2 3 4 15 12
  3 4 5 28 20
  4 5 6 45 30
  5 6 7 a 42
  6 7 8 91 56
  3*4 + 3*1=15
  4*5 + 4*2=28
  5*6 + 5*3=45
  6*7 + 6*4=a=66=answer...
  7*8 + 7*5=91
  3*4+3*1=12
• 13 years agoHelpfull: Yes(2) No(1)
• a=42 + 6*(6-2) = 66
  a=last no. + 2nd no.*(2nd no. - 2)
• 13 years agoHelpfull: Yes(1) No(1)