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+11/99) - 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)

= - 17/819