4.9乘1.4怎么简算

4.9*1.4
=(5-0.1)*1.4
=5*1.4-0.1*1.4
=7-0.14
=6.96

4.9×1.4=（5-0.1）×1.4=5×1.4-0.1×1.4=7-0.14=6.86

(5-0.1)*1.4
=5*1.4-0.1*1.4
=6.86

5乘1.4减1.4=5。6

把4.9看成5-0.1，把1.4看成1+0.4或者1.5-0.1或者15*0.1-0.1（利用加半加零思想），具体步骤就不写了。