Over what distance is transporting a box of DVDs faster than a 100Mbps connection?

Question

This questions blends a bit of math and computer science, but I thought this would be the most appropriate SE board for it (if not please guide me to what you believe is the most appropriate board for this, as it's not programming related it doesn't belong to StackOverflow)

For a box of ten 4.5 GB DVDs, calculate for what range of distances transporting these at an average speed of 50 mph provides a bandwidth in excess of 100 Mbps.

To me this question doesn't make sense, I'm misunderstanding something:

• 50 mph is roughly 8 miles per second (mps) (EDIT: this is wrong, I divided by 60 instead of 3600).

• 45 GBytes is 360 Gbits, which is 360'000 Mb

What I understand is this:

• This box of DVDs is transporting 360'000 Mb at 8 mps. In other words, over a distance of 8 miles it's bandwidth is 360'000 Mbps.

• The speed is constant, so this box bandwidth is 360'000 Mbps?

• If the above point is true, then this is always faster than 100 Mbps.

I've clearly misunderstood something about my lecturer's question (unless the answer he wants is over a range of 0 to infinity, which is unlikely).

Answer 1

$50$ mph is $50$ miles per hour, which is quite different from $8$ miles per second. You have calculated the number of bits correctly. How long does this take to transmit at $100$ Mb/second? How far can you drive in that time?

The point is that over the data link, the time is constant. Driving, the time is proportional to the distance. Driving will win up to some distance, after which the data link will win. You are asked to find the crossover point.