You want to leave a 10% tip on a meal that cost $1000.

First, convert the 10% to an actual number that can be used in a calculation. For percents,this is always done by simply dividing the percent (in this case 10%) by 100%.So, the conversational term "10%" becomes 10% / 100% = 0.10 in terms of a real mathematical number.Second, you need to find out what 10% of your $1000 meal cost is.This is always done by multiplying 0.10 by $1000.00, or

0.10 x $1000.00=$100.00. So, the amount of tip you are going to leave is $100.00.

This makes the total cost of your meal (to write on your charge slip or other payment)

$1000.00 + $100.00 = $1100.00.

15% is 10% + 5%(or 0.15 = 0.1 + 0.05, dividing each percent by 100). Thinking about it this way is useful for two reasons. First, it's easy to multiply any number by 0.1; just move the decimal pointleftone digit. For example, 75.00 x 0.1 = 7.50, or 346.43 x 0.1 = 34.64 (close enough). Second, 5% is exactly half of 10%. So here's how this quick and easy method works:Take the total cost of your meal, $1000.00 and multiply it by 0.1 by sliding the decimal to the left one digit to get $100.00 (you can do this in your head at the table). $100.00 is 10% of your meal cost. But the proper tip to leave is 15% (you need to throw in another 5%).

The additional 5% is just half of the 10% amount. What is half of $100.00? About $50.00. (Finding half of a number is also something you can do in your head at the table.) So, the total tip to leave is the 10% amount PLUS the 5% amount (for a 15% tip) or $100.00 + $50.00 = $150.00 .

The general rule here is:

- Find the number that results from sliding the decimal point of the meal's cost left one digit,
- and add on another half of this number.

That's your tip!