The english phrase "rule of thumb" referes to an approximate method for doing something, based on practical experience rather than theory. An example of a rule of thumb would be: changing the oil of a car every certain number of milles traveled. "<em>To start with, change the oil every 5000 or 6000 miles". </em>In the example you can notice that is not strictly accurate or reliable for every situation.
If each pound costs six dollars, and you have $66 available, you have to think: how many six-dollar pounds will fit in $66. That is 66 divided by 6. ANSWER: 11 pounds.
