if five times the 5th term of an A.p. is equal to 8 times its eighth term, then 13th term is ?

• ANS:
  0
  soln:
  given, 5*t5=8*t8
  ==> 5(a+4d)=8(a+7d)
  ==> 5a+20d-8a-56d=0
  ==> 3a+36d=0
  ==> a+12d=0
  ==> a+(13-1)d=0
  w.k.t, a+(n-1)d=tn
  ==> a+(13-1)d=t13==0.
  
• 11 years agoHelpfull: Yes(1) No(0)
• usually Arithmetic progression is in the form of
  a,a+d,a+2d,a+3d,a+4d,a+5d........
  a is first term,a+5d is 5th term and a+13d is 13th term
  given 5(a+5d)=8(a+8d)
  5a+25d=8a+64d
  ==>3a+39d=0
  ==>3(a+13d)=0
  ==>a+13d=0
  hence 13th term is 0
• 11 years agoHelpfull: Yes(0) No(0)