With so many people having a smartphone in their pocket -- a calculator that can help determine discounts in stores, calculate a tip percentage in restaurants, or balance a checkbook in a snap -- is it really useful to be able to do fast math in your head? Many still say yes. You may not always have a calculator handy, or you may have your hands full or no cell service. Before you wonder just how useful that high school algebra class was, see if you know these best math tricks.


1. Calculate Percentages in a Flash

Instead of worrying about how much to tip at a restaurant, or the dollar amount of your favorite clearance sale, use this fast trick to determine percentages. First, multiply the first number by the second number. For example, 30 percent of 50 is 30 x 50. Keep in mind that percentages are a fraction of 100, so you'll move the decimal places two points to the right. So, for 30 percent of 50, you multiply 30 x 50, which is 1500. Move your decimal point two places to the right, and you'll see that 30 percent of 50 is 15.

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