Question

The sum of all integers between 81 and 719 which
are divisible by 5 is

Answer 1

The Least number greater than 81 which is Divisible by 5 is

85

while the largest number smaller than 719 i and Divisible by 5 is

715

so a=85

d=5

an=715

an=a+(n-1)d

715=85+(n-1)5

715-85=n-1)5

630/5=n-1

n=127

sn=n/2(a+l)

sn=127/2(85+715)

sn=127(400)

sn=90800