我们在生产和生活中所接触到的数,有些不是完全精确的而只是表示量的近似值的数。如我们在计算圆的周长和面积时所用到的圆周率(π)3.14就是它的近似值。从计数、测量和计算中,有时候我们虽然可以得到准确数,但由于没有必要知道得那么精确,或者所得到的准确数的某一位上的数没有实际意义,这时我们就取它的近似值;有时候我们不可能得到准确数,就按照所需要的精确度用近似值来代替。如何取一个数的近似值呢? 取一个数的近似值,首先要确定实际所需要的精确度,然后再按所需要的精确度依一定的法则去取这个数的近似值。所谓实际所需要的精确度,这是要根据不同事物的具体需要来确定的。例如统计水稻的单位面积产量一 Some of the numbers that we come across in our production and life are not exactly exact, they are simply numbers that approximate the quantity. As we have used in calculating the circumference and area of ​​the circle (π) 3.14 is its approximation. Sometimes counting, measuring and calculating, although we can get the exact number, but because there is no need to know so precise, or accurate number of the resulting number of a bit of no practical significance, then we take it Approximation; sometimes we can not get the exact number, we just use the approximation instead. How to take a number of approximations? To take a number of approximations, we must first determine the accuracy of the actual needs, and then press the required accuracy according to a certain law to take this approximation. The so-called actual required precision, which is based on the specific needs of different things to determine. For example, statistics of rice yield per unit area