三亿零三十万零三十写作(300300030 ),改写成用"万"作单位的数是（30030.003 ）万,精确到亿位是(3亿 )1.简便计算 (1/3-1/6+1/4)*12......3/3/7-3/7/3(1/3-1/6+1/4)*12=1/3*12-1/6*12+1/4*12=4-2+3=5