Avg rotational latency = 5 msec // Time to reach the start of that track
Avg. seek time = 5 msec // Time to move onto particular track
For Successive sectors:
= avg. seek time + time to get to starting sector(or avg rotational latency ) + rotational latency for req. no of sectors
= 5ms + 5ms + [ (12 tracks * 10msec rotational latency) + (time to read 32 sectors of 13th track) ]
= 10 + 120 + 5
= 135msec
For Random sectors:
To read one sector = avg. seek time + time to get to starting of sector(or avg rotational latency ) + rotational latency for one sector
= 5ms + 5ms + 10/64
Total time to read 800 sectors = 800 * [ 5ms + 5ms + 10/64 ] = 8125 msec