Question

find
the number of
terms of the series
21, 18, 15 ,12. which must be
taken to give a sum of Zero
​

Answer 1

here using A.P formula

An = a+(n-1)d

An = 21 + (n-1) -3

An = 21 + 3n - 3

An = 18 + 3n

n = 9

9 term will take it to give a sum of Zero.