Question

What is the number of the series 5,7,9....1,020

Answer 1

Answer :

n=30

Explanation :

Sn=1020

a=5

d=2

so ,

Sn=n/2[2a+(n-1)d]

1020=n/2[8+2n]

4n+n^2=1020

n^2+4n-1020=0

n(n-30)+34(n-30)=2

n+34 or n-30

n=-34 or n=30

n ≠ -34

n=30