Shortcut trick for addition of common difference in series of numbers.

Example, 1) 49 + 55 +  61 + 67 + 73 = ?
             ⇒ Step 1) Add the smallest number to biggest number that is 49 + 73 = 122.
                  Step 2) Then multiply the sum with 5.....( here we add total 5 numbers so multiply                                      result of first step with 5) i.e. 122 × 5 = 610.
                  Step 3) At last divide the result of second step by 2. i.e 610/2 = 305
                  So we get, 49 + 55 +  61 + 67 + 73 = 305.

                2) 25 +30 + 35 + 40 + 45 + 50 + 55 + 60 + 65 = ?
               ⇒ Step 1) 25 + 65 = 90
                   Step 2) 90 × 9 = 810
                   Step 3) 810/2 = 405
                   So we get, 25 +30 + 35 + 40 + 45 + 50 + 55 + 60 + 65 = 405.