In this deck, we'll cover some essential skills for handling money and other values. You'll learn how to calculate percentage increases and decreases, how to work backwards to find an original price, and how to calculate simple interest on savings or loans.

Let's start with percentage change. A percentage increase makes an amount bigger. For example, if your wages go up by 5 percent, you get more money. A percentage decrease makes an amount smaller, like when an item has 20 percent off in a sale.

To make these calculations quick, we use something called a decimal multiplier. The original amount is always 100 percent. For an increase, we add the percentage. So, a 10 percent increase is 100 percent plus 10 percent, which is 110 percent.