Rounding numbers - is a mathematical operation that allows you to reduce the number of digits in the number, replacing it with an approximate value. Rounding numbers are used for convenience in the calculations.
After all, I do not want to confuse and bother with numbers that are digits after the decimal point five, or even more. There are a few rules of rounding:
If the first digit you want to discard,greater than or equal to 5, the latter figure, which remains - is incremented by one. Example: take the number 25.274 and round it to the nearest tenth. The first cast by digit - 7, more than 5, so it is stored figure - 2 increments. That is, it turns round number - 25.3.
If the first digit you want todrop, less than 5, then the increase in last stored numbers are not happening. Example: 38.436 rounded to the nearest tenth. The first number that we want to discard - 3, is less than 5, so it is stored number - 4 is not increased. It remains to round number - 38.4.
If the figure we want to be dropped is 5, butfor it has no significant digits, the last digit is stored by the same, if it is even, and if odd, then incremented. Example 1: 42.85 is the number, round it to the nearest tenth. Discard figure 5, and, as for there is no significant digits, and the last stored by the figure 8 - even, it remains unchanged. That is, we get the number of 42.8.
Example 2: 42.35 number rounded to the nearest tenth. Drop figure 5, it is not at a significant digits, but the latter retains the number 3 - odd, she, respectively, increased by one and becomes even. Get 42.4.