Imagine that you are buying a T-shirt for , a pair of socks for and a belt for . The cashier charges you . You feel that this is too much - but how do you know?
One way of finding out whether you have been over-charged is to estimate what the total amount should be. Round the different prices into easier numbers - is approximately , is approximately and is approximately - and you can do the calculation quickly in your head.
This is almost less than the cashier asked for, so obviously you have been over-charged.
The symbol means 'approximately equal to'.
By rounding the actual values to more manageable numbers, you can estimate the answers to many problems: