Find the number of terms required to make the sum equal to zero for the following series 80, 75, 70, ...
Answers
Answered by
1
Sum =n/2(a+l)
Where n is the no. Of terms, a is the first term and l the last term.
A/Q
n/2[2a +(n-1)d]=0
as l=a+(n-1)d
=>2a+(n-1)d=0
As n cannot be 0
=>2*80+(n-1)(-5)=0
So, (n-1)(5)=160
=>n-1=32
=>n=33(answer)
Similar questions