How long will it take to transfer a2GB file at 56 Mbps?

30 min 476195 sec (30.47min).

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I worked it out as:

100MB = 100*1024*1024*8 = 838,860,800 bits

838,860,800/1024 = 819200 Kb

Thus it will take approximately 819200/56 = 14629 seconds (to the nearest second) = 4.06 hours approximately (if it runs at full speed the whole time)!

[Answer is assuming 56kbps means 56 kilobits per second (not Kilobytes). If you meant 56 kBps then the first answer above would be right.]