Question

(143分之1+77分之1+91分之1)除以(99分之20+9分之1)—91分之2=？ 请用简便运算！！！！！

Answer 1

(1/143+1/77+1/91)÷(20/99+1/9) - 2/91
= [7/(11×13×7)+13/(77×13)+11/(91×11)]÷(20/99+11/此燃差99) - 2/91
= 31/(11×13×7)÷31/(9×11) - 2/91
= 1/(13×7×9) - 2/(13×7)
= 1/(13×7×9) - 18/(13×7×9)
= - 17/(13×7×9)
= - 17/森皮段雀819

追问

你的思路是怎样的？

追答

(1/143+1/77+1/91)÷(20/99+1/9) - 2/91
= [7/(11×13×7)+13/(77×13)+11/(91×11)]÷(20/99+11/99) - 2/91 【除号前后分别通分】
= 31/(11×13×7)÷31/(9×11) - 2/91
= 31/(11×13×7) × (9×11)/31 - 2/91 【除法变乘法：除数分子变分母，分母变分子】
= 9/(13×7) - 2/91
= 9/91 - 2/91
= 7/91

Answer 2

(1/143+1/雀橘77+1/91)÷(20/99+1/野闷9) - 2/91
=[(7+13+11)/（13×11×7）】÷1/9（颂岁弯20/11+1）-2/91
=31/（13×11×7）÷31/(9×11) - 2/91
=31/（13×11×7）×(9×11)/31-2/91
=9/91-2/91
=7/91

追问

你的思路是怎样的？

追答

(1/143+1/77+1/91)÷(20/99+1/9) - 2/91
=[(7+13+11)/（13×11×7）】÷1/9（20/11+1）-2/91(被除数通分,除数提取公因数1/9）
=31/（13×11×7）÷31/(9×11) - 2/91
=31/（13×11×7）×(9×11)/31-2/91（除法变乘法，除数变倒数）
=9/91-2/91
=7/91=1/13