the sum of certain no. of terms starting from first of an AP 25,22,19_,_,_,_,is 116 . find the last term
Answers
Answered by
1
Use the sum of an AP formula
n/2 {2a + (n-1) * d} = sum
where n = nth term, a = 1st term and d=common difference
n/2 {2*25 + (n-1) * (-3)} = 116
Solving the equation we will get 2 values for n = 58/6 and 8
since the nth term has to be an integer, the only permissible value has to be 8
Now we need to find the 8th term. You can manually do that by subtracting 3 from each of the term till the 8th term or you can use the formula.
a+(n-1) * d
=25 + (8-1) * (-3)
=4
Similar questions