The sum of the first and the 9th of an arithmetic progression is 24. What is the sum of the first nine terms of the progression?

• ans=108
  a+a+8d=24
  2a+8d=24
  sum of 9 terms=9/2*(2a+8d)=108
• 11 years agoHelpfull: Yes(2) No(0)
• Let us assume that first term is a,and 9th term is a+8d.
  sum of the first and 9th term is 24,2a+8d=24
  number of terms is 9,so that sum of 9 terms is = 9/2(2a+8d)=9/2(24)=108
• 11 years agoHelpfull: Yes(1) No(0)