1. Can you have MORE than 100%?
Yes. 200% of something is double what you started with
2. If someone scores a mark of, say, 72 out of 80 in a test, how is it changed to a percentage?
Multiply the 72 by 100 and then divide by 80.
3. What is the quickest way to increase, say, 120 by 5%?
You could find 5% of 120 and then add it on to 120 but... the QUICKEST way is to multiply 120 by 1.05