7.8*5.6+3.9*8.8的簡算方法

7.8*5.6+3.9*8.8的簡算方法


7.8×5.6+3.9×8.8
=7.8×5.6+3.9×(7.8+1)
=7.8×5.6+3.9×7.8+3.9
=7.8×(5.6+3.9)+7.8×0.5
=7.8×(9.5+0.5)
=7.8×10
=78



3.7×9.8簡算


3.7x10-3.7x0.2= 37-0.74=36.26



13分之7(19分之14-13分之6)簡算幫我!


13分之7-(19分之14-13分之6)
= 7/13 + 6/13 -(14/19
= 1-14/19
= 5/19



2/3-7/12+9/20-11/30+13/42-15/56簡算


2/3-7/12+9/20-11/30+13/42-15/56
=2/3-(1/3+1/4)+(1/4+1/5)-(1/5+1/6)+(1/6+1/7)-(1/7+1/8)
=2/3-1/3-1/8
=1/3-1/8
=5/24