Considering the fact 8 bits = 1 byte, how will it take to download a 1 MB file browsing at one megabits per second(1mb/s)? Please show all your working.

Assuming (as usual) small b means bit and Capital B means byte.

speed = bits/time = 1Mb/s

bits = 8*1Mb

Substitute that bits in the equation above, you get:

8Mb / time = 1Mb/s

Solve for time:

time = 8Mb / (1Mb/s) = 8 s

So it should take 8 seconds. Notice that M (which is usually 1024*1024, or 1000*1000) simply cancels out.