1. If someone scores a mark of, say, 72 out of 80 in a test, how is it changed to a percentage?
Muliply the 72 by 100 and then divide by 80.
2. 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
3. How is the cost of an item increased to include the GST component?
(Goods and Services Tax, GST, is a tax used in some countries − added to the price of goods or services bought.)
Multiply the cost by 1.15 (this increases it by 15%)
4. How do you calculate the cost of an item without GST?
Divide the cost including GST by 1.15