I saw the question bellow in a Computer Organization Practice Book for University exams.

`Its given that, a magnetic disk has the following specifications:`

Number of tracks = 1024

Number of sectors/track = 512

Bytes/Sector = 512

Disk Rotation Speed = 7200 RPM

Seek time = 9ms

The question given:
`What is the data transfer rate?`

The answer given: `30GBPS`

My answer: `30MBPS`

My method of doing it:

Rotation speed: 7200RPM

So, 7200 rotations in 60 sec

1 rotation in 60/7200 sec.

Now, in 1 rotation only 1 track is read

1 track = 512 sectors = 512*512 bytes.

So, in 1 rotation 512*512 bytes is read.

i.e. In 1 Rotation 256 KB is read [ since, 512*512 bytes =256*1024 bytes ]

Thus, In 60/7200 sec 256 KB is read

In 1 sec 256*7200/60 KB is read

i.e 256*120 KB = 30 * 1024 KB = 30 MB

So, data transfer rate according to me: 30 MBPS.

But the explanation given in the book considered that in 1 rotation all tracks are read,

i.e In 1 rotation 1024*512*512 bytes is read and this is how they are getting the answer as 30 GBPS.

**Kindly help me out here. Am I right? Or is the book correct?**