Illustration Decimal places (d.p.) refer to the digits to right of the decimal point. For example ‘23.845’ have 3 decimal places. The numbers we get from a computation often contains worthless digits that must be thrown away. Whenever we do this we must round our answer to the required decimal places.
Rule 1 If the first digit to be discarded is greater than 5, or a 5 followed by a non zero in any of the decimal placed to the right, then round up by the last digit retained.
Rule 2 If the first digit to be discarded is less than 5, round down by the last digit retained. Write -6.0439 to 2 d.p. Here 3 is first discarded digit and 4 is the last retained digit. Since 3<5 so we round down and hence result will be -6.04.
Rule 3 (Important) If the first digit to be discarded is equal to 5, always round to the nearest even number.
Do not Forget to… When you were asked to write a number to for example to 3 d.p., consider the first 4 d.p. places during the computation and write the end result to 3 decimal places. Got It?
For example, here is a series of addition and result is required to 2.d.p