(a)Formula: divide the speed value by 3.6 = 54/3.6 54 kilometres per hour = 15 metres per second = 15 m/s b)Formula: multiply the speed value by 3.6 = 6x3.6 6 metres per second = 21.6 kilometres per hour = 21.6 km/hr (c)Initial velocity, = 25 m/s Final velocity, = 10 m/s Time taken, = 5s Acceleration= v-u/t= 10-25/5 = -15/5= -3m/s²