How many terms of the sequence -14, -10, -6,…so on, to make a sum of 360? A)15 B)20 C)16 D)18

• Ans: D).18
  Sn=n/2(2a+(n-1)d)
  hence 1st number is -14=a,,,, difference of 2numbers is 4=d,,,,, make sum of 360;;
  =>n/2(2(-14)+(n-1)4)=360
  =>n/2(-28+4n-4)=360
  =>4n/2(-7+n-1)=360
  =>2n(-8+n)=360
  => 2n^2-16n=360;
  =>n^2-8n=180;
  =>n^2-8n-180=0;
  =>n^2-18n+10n-180=0;
  => n(n-18)+10(n-18)=0;
  => therefore n=18 or n=-10 , here always take postive value
  so ans: D).18
  =>
• 5 years agoHelpfull: Yes(3) No(0)
• The answer is 15
• 5 years agoHelpfull: Yes(0) No(3)