Find out the Sum

           What is the sum of all numbers between 100 and 1000 which are divisible by 14?

Answer:   S = 112 + 126 + …………………….. 
                S =14 (8 +9+ …………………………71)

                S = 14(8+71) (71 – 8 +1) / 2

              S = 7(79) (64) = 35392