Step 1: Construct a imaginary figure according to given hints

          EXAMPLE: Let PQ be a chord of a circle with centre O and radius 13cm  

                              such that PQ = 24cm.

Step 2: Draw (OM) perpendicular line to the chord (PQ) and join the center and the end point of the chord.

Step 3: Find the  base of the right angle triangle

  NOTE: The perpendicular from the centre of a circle to a chord bisects the  chord.

                EXAMPLE ∴ Base PM = 12cm

Step 4: Recall the Pythagoras theorem to calculate the  unknown value

          NOTE: (Hypotenuse)^2 = (height)^2 + (Base)^2

Step 5: Substitute all the known values in the Pythagoras formula and simplify the equation.

EXAMPLE:  In △OMP, we have

                   OP= OM2 + PM2

                  ⇒ 13= OM+ 122

                        ⇒ OM = 5cm.                                                                        

      Hence, the distance of the chord from the centre is 5cm.