Quick and easy method to mentally find 2 1/2 percent of a any number.

Step 1) ; Choose number (Start with 2 digits and advance to 3 with practice)
Step 2) ; Divide by 4.
Step 3) ; Move decimal point one place to the left.

Examples, 1) If the number selected is 86.
                  ⇒  Divide 86 by 4
                       86/4 = 21.5.
                  Move decimal point one place to the left. i.e. 2.15.
                  So we get, 2 1/2 % of 86 = 2.15.

                   2) If the number selected is 648.
                  ⇒  Divide 648 by 4
                       648/4 = 162
                  Move decimal point one place to the left. i.e. 16.2.
                  So we get, 2 1/2 % of 684 = 16.2.