19.6/(9.8/0.4)簡便計算6.3/1.8簡便計算

19.6/(9.8/0.4)簡便計算6.3/1.8簡便計算

19.6/(9.8/0.4)=19.6*0.4/9.8=2*0.4=0.8
6.3/1.8=7*0.9/2*0.9=7/2=3.5