Question

find the sum of 7+101/2+14+.......84

Answer 1

Answer:

Step-by-step explanation:

a=7. d=7/2

an=a+(n-1)d

84=7+(n-1)7/2

84-7=(n-1)7/2

77=(n-1)7/2

77×2/7=n-1. (Here 7 divides with 77)

11×2=(n-1)

22=n-1

n=22+1

n=23

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

Sn=23/2 (2×7+(23-1)7/2)

Sn=23/3 (14+22×7/2) (2 divides 22)

Sn=23/2 (14+11×7)

Sn=23/2 (14+77)

Sn=23/2 (91)

Sn=2143/2

Hope..... this solution would help u.....