已知：[（11.2-1.2÷□）×4+51.2]×0.1=9.1，那么□=．

Question

已知：[（11.2-1.2÷□）×4+51.2]×0.1=9.1，那么□=______．

Answer 1

将□看作未知数x，
则原式变形为：
[（11.2-1.2÷x）×4+51.2]×0.1=9.1
[（11.2-1.2÷x）×4+51.2]×0.1÷0.1=9.1÷0.1
            （11.2-1.2÷x）×4+51.2=91
       （11.2-1.2÷x）×4+51.2-51.2=91-51.2
                 （11.2-1.2÷x）×4=39.8
              （11.2-1.2÷x）×4÷4=39.8÷4
                        11.2-1.2÷x=9.95
                   11.2-1.2÷x+(1.2)/(x)=9.95+(1.2)/(x)
                               11.2=9.95+(1.2)/(x)
                          11.2-9.95=9.95+(1.2)/(x)
                               1.25=(1.2)/(x)
                            1.25×x=(1.2)/(x)×x
                              1.25x=1.2
                        1.25x÷1.25=1.2÷1.25
                                  x=0.96．
故答案为：0.96．