The most basic rule is that when the number is need to be rounded, you must look at the previous figure and make a comparison with the digit 5. If the figure is greater than 5, it will be rounded to the larger number, and if it is less than five, in this case, it would be rounded to that exact number.
If the figure we observe is equal to digit 5, we have to look at the figure on next to it. In this case, the same rule applies.
Consider the following example:
If there is a number X,x,y,z, where X is an integer, and x,y,z its decimal point, then the number is rounded to the decimals carried out according to the following rules:
X, x,y,z < 5, a decimal point is the same,
X, x,y,z > 5 decimal point is increased by 1,
X, x,y,z = 5, and x,y,z are different from zero, then number X is rounded at X,x,y,z + 1.
When we are rounding off numbers, we have to know that some digits can be safe, and some of them are unsafe. Safe figures are those which contain accurate information about the value of the size we consider. When value is uncertain and when an error can happen to an error during an mathematical operation, digits are unsafe.
In mathematics, the rule is that you should perform mathematical operations with numbers with more than three decimal digits. This is done only in special cases. When you add and subtract, the obtained results should be maintained on same point as much as there are digits in number with the smallest number of digits. The same goes for multiplication and division.
0.0153 + 0.245 + 1.72 = 1.92 3 ≈ 1.92
If we want to perform multiple operations of multiplication and division, the point in the result will increase by one.
In the end, it is important to remember the following rule: If the number we want to eliminate in the decimal point is five, and after that there are no more digits different from zero, then we observe if the digit is even or odd. In this case, if the last digit is even, the numbers remains the same. If the number is odd, the last digit will be increased by one.