What ideas do you need to remind yourself when working with percentages

To find 1% of a number, divide it by 100
To find 10% of a number, divide it by 10
To find 5%, find 10% then half it
To find 25% of a number, divide it by 4
To find 50% of a number, divide it by 2
To find 20%, 30%, 40%, 60%, etc, find 10% and then multiply by 2, 3, 4, 6, etc.

~ Hope this helps!