一般常用数值范围为０．１－１０００，尾数有３个以上“０”的整数和小数点后面有３个以上“０”的纯小数，均可改为“ × １０ｎ”（ｎ为正、负数），但属于有效数宇的“０”必须写出。例如：已知４８０００００这个数有３位有效数字测应写作４．８０×１０６或４８０×１０ Commonly used numerical range of 0.1-1000, the mantissa has more than 3 “0” integer and decimal point after more than 3 “0” pure decimal, can be changed to “× 10n” (n is positive and negative) , But the “0” that belongs to the significant number must be written. For example: known 4800000 this number has 3 significant figures should be written 4.80 × 106 or 480 × 10