Someone asks you: "How much data can you put on a 3.5" floppy"

You say: "1.44 MB"

Wrong!

Here's why: 80 tracks * 18 sectors * 512 bytes * 2 sides = 1474560 bytes / 1024 = 1440 KB / 1024 = 1.41 MB my friends!!!

Now who was the full to do all the above calc and think 1 MB is 1000 KB in the last step?