Step 1:  Examine the given question

              Let E be the event that 'the music is stopped within the first half-minute'.

                The outcomes favourable to E =  The distance from 0 to \frac{1}{2} = \frac{1}{2}   

                The total distance = Fom 0 to 2 = 2

              Therefore, the probability that the music will stop within the fist half

                              P(E) = \frac{Dis\tan ce\ favourable\ to\ the\ event\ E}{Total\ dis\tan ce\ in\ which\ outcomes\ can\ lie}

                                            = \frac{\frac{1}{2}}{2} = \frac{1}{4}