Question

15 + 17 + 19 + ....51​

Answer 1

Answer:

a=15,d=17-15=2,l(an)=51

l=a+(n-1)d

51=15+(n-1)2

51-15=(n-1)2

36/2=n-1

18+1=n

n=19

we have to find Sn

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

S19=19/2(30+(19-1)2)

S19=19/2(30+36)

S19=19/2×66

S19=19×33

S19=627