worldof20something

Sometimes it’s okay to pull out that trusty calculator at a restaurant to figure out how much you need to tip.  Close friends and family probably don’t mind.  But other times, it’s really not okay.  Certain circumstances where you need to impress your company, such as business outings, are definitely not the time to show off your new TI-91.

It’s time to learn how to calculate a tip using nothing more than the power of your brain.  And once you try it a few times, you’ll be surprised how easy it is to do.

Let’s start simple: the bill for dinner is $20.00.  Here’s what we do to get to 15%:

1. 10% of $20.00 can be found by moving the decimal one place to the left, which makes $2.00.
2. 5% is half of 10%, and half of $2.00 is $1.00.  Therefore, 5% of $20.00 is $1.00.
3. We’ve found 5% and 10%, so add them together to get your 15% tip!  $2.00 and $1.00 added together makes $3.00, which is a 15% tip on a $20.00 bill.

Let’s try something a little harder: the bill for dinner is $136.45.  Here’s what we do to get to 15%:

1. To get 10% of $136.45, just move the decimal one place to the left.  That makes $13.64… (you can ignore any numbers after the second one right to the decimal because that’s all we need for money terms).
2. 5% is half of 10%, so we need to find half of $13.64.  Instead of trying to figure out what this is, round up to $14.00.  Half of $14.00 is $7.00, so we can say that 5% of $136.45 is about $7.00.  (Just so don’t feel too cheated about rounding up, doing this increased the total by less than 20 cents.)
3. Now that we know 5% and 10%, just add them together to get the 15% tip.  Adding $7.00 to $13.64 is $20.64.  $20.64 is a 15% tip on a bill of $136.45.

Does 15% sound stingy to you?  If so, you’re lucky, because finding 20% is even easier.  Just find 10% by moving the decimal of the total bill one place to the left.  Take that number and add it to itself; that’s 20%.

This may all seem very complicated at first, but just try it a couple of times and you will get the hang of it!  I know you won’t mind leaving your calculator at home.

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