Question

1+3+5+7+.....+35 find the sum of value

Answer 1

Answer:

a=1

d=5-3

=2

n=?

tn=35

tn=a+(n-1)d

35=1+(n-1)2

35-1=2n-2

34=2n-2

34+2=2n

36=2n

36÷2=n

18=n

n=18

therefore,

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

Sn=18/2[2.1+(18-1)2]

Sn=9[2+(17)2]

Sn=9[2+34]

Sn=9×36

Sn=324