Rounding is an accurate counting reservation method, which is essentially the same as other methods. But the special point is that rounding can make the difference between the reserved part and the actual value not more than half of the last order of magnitude.
If the probability of 0 ~ 9 is equal, the error sum of this method is the smallest for a large number of reserved data. This is why we use this method as the basic booking method.
When using scientific computers for construction work, we often encounter such a situation: sometimes there are several decimal points on the left side of the integer of the answer. For example, short side 255 divided by long side 1005 = tan 0.438+03.
Similar to this situation, it will be more complicated to calculate the size and side with these decimal points as reference tan values. So in order to properly remove similar decimal points without affecting the actual dimensional accuracy, I will introduce the rounding calculation method in mathematics here.
Usually, the drawings that carpenters come into contact with are metric, and the area they make ranges from tens of millimeters to dozens of meters. As long as the decimal point is appropriately deleted according to the actual size, and the error is less than one millimeter, the rounding method should be implemented. Where should rounding be implemented?
In millimeters, if it is in the third place, we will round it off in the fourth place. Look at the fourth place first: if it is 4 or less, we will discard it; If it is 5 or greater, it is also discarded, but 1 should be added to its left cell. This method is called rounding.
Take another example above, multiply the value of tan by the big side, and you can get the value of the small side. Assuming that the value of tan remains the same, and the value of the big side is changed to 3000, which is the fourth place in millimeters, then it is enough for us to take the four decimal places of tan as the operation value.
The fifth digit is 3, which is omitted because it is less than 4, that is, 0.2537 times 3000=76 1. 1. If the decimal point of the answer is less than 1mm, it should be deleted and only 76 1mm should be taken.
But in rounding, the probability of rounding is four out of nine, and the probability of entering one is five out of nine, which is different. Therefore, there is a saying of "four families and six people". Among them, if 5 needs to be rounded, if the previous number is odd, enter 1, and if it is even, it will be truncated.