42+98×21簡算

42+98×21簡算


42+98×21
=2×21+98×21
=21×(2+98)
=21×100
=2100



84+42*98怎麼簡算


84+42*98
=42*(98+2)
=42*100
=4200



0.7×98簡算


0.7×(100-2)=70-1.4=68.6