(1)68.457+236.51-9.753=
(1)8.475+20.3-9012= (2)5.25x103-4.2x102=
用有效數(shù)字運算規(guī)則計算下列各式: ⑴2.00x4.00+50.0x1.00+20x0.1 ⑵6.80x103-20