Question

The sum of all numbers between 100 and
1000 which is divisible by 13, is​

Answer 1

37674

Explanation:

Note that the numbers form an arithmetic sequence

`100/13=7...9\\1000/13=76...12\\\therefore The\ sum \\=13*8+13* 9+13* 10+...+13* 76\\=13* (8+9+10+...+76)\\=13* ((8+76)*(76-7))/(2)\\=37674`