This is an other popular trick. A lot of the times called the Restaurant Tip because it is 15% of the total bill.

Obviously the number you will get when multiplying by 15 is 100 times bigger than what the 15% is.

To this you need to use a 3 step approach.

Let us use 34 for example

**1) ** Find what the number multiplied by 10 is.

This is very easy as you simply add a 0 at the end.

**34×10 = 340**

**2) ** Find what the number times 5 is.

To this fast find what that number times 10 is and divide by 2. We did this in the previous step.

**340/2= 170**

**3)** Add these 2 numbers together

**340+170=540**

For finding 15% (0.15) of a number simply divide this number by 10.

View bellow a couple of examples