Question

The sum of all natural numbers between 500 and 1000 which are divisible by 13 is
(a) 28,405
(b) 24,805
(c) 28,540
(d) none

Give proper explanation

Answer 1

smallest number divisible by 13 is 507

Biggest number divisible by 13 is 988

Now Using AP formula

t=a+(n-1)d

t=988 a=507 d=13

988=507+(n-1)13

481=13n-13

n=494/13

n=38

Using AP sum formula

Sum =n/2 (a+t)

sum=38/2 (507+988)

sum=19×1495

Sum =28405

Option A