数学计算题. 要用简便计算 .. 呵呵有点麻烦,写清楚就加分!

题目

数学计算题. 要用简便计算 .. 呵呵有点麻烦,写清楚就加分!
5×（3/5+2/7）×7
666×7+58×111
4/9×13+7/9÷1/13-13
1000÷0.4÷1.25÷8÷2.5
40/29×18-11×18/29+92
101×99×999+999
8又3/5×2.7+62×14%+35×0.86
121×27+121×60+121×16+79×91+12×79

答案

5×（3/5+2/7）×7
=5X5/3X7=2/7X7X5
666×7+58×111
=111X6X7+58X111
=111X(6X7+58)
4/9×13+7/9÷1/13-13
=4/9×13+7/9X13-13X1
=(4/9+7/9-1）X13
1000÷0.4÷1.25÷8÷2.5
=1000/(0.4X1.25X8X2.5)
=1000/[(0.4X2.5)X(1.25X8)]
40/29×18-11×18/29+92
=40X(1/29X18)-11X(1/29X18)+92
101×99×999+999
=(100+1)X(100-1)X(1000-1)+(1000-1)
8又3/5×2.7+62×14%+35×0.86
=8.6X2.7+62X0.14+3.5X8.6
121×27+121×60+121×16+79×91+12×79
=121X(27+60+16)+79X(91+12)