Everyday Math: Ladies, Tip Your Waiters

We’ve all been there – the check arrives, it’s time to figure out the tip, and all of a sudden you can’t remember any of the math you learned in high school. No worries! You don’t need to whip out the calculator on your cell phone to make sure the waitstaff get what they deserve. Here are a few sneaky tricks to figure it out in your head, without having to multiply by any decimals!

If you’re feeling especially generous, the easiest tip to calculate is 20% (whether or not to include drinks or tax is between you and Emily Post). Either divide the total by 5, or drop the last digit from the total and multiply by 2. For example, let’s say the total is $30.00. 30.00 / 5 or 3.00 x 2 = $6.00.

A 15% tip is also relatively easy. Drop the last digit from the total like in the example above, divide that number in half, and then add those two numbers together. For that same $30 ticket, 3.00 + 1.50 = $4.50.

Let’s say you want to tip somewhere between those two numbers. Dividing the total by 6 will give you a 16.7% tip. (30.00 / 6 = $5.00) Or if you want to be fancy and tip exactly 18%, you can still do it without too much trouble. Knock off the last digit, then knock off another digit and subtract this number from the first. This will give you 9% of the total, so double it for 18%. 3.00 – .30 = 2.70; 2.70 x 2 = $5.40.

The same tricks work with any number, not just even dollar amounts (though it may be easier to ignore the change for larger amounts since you’ll likely round the total off to the nearest dollar anyway). Not that bad, was it?

This post originally appeared on Persephone Magazine on October 5, 2011.

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