阅读辛弃疾的《鹧鸪天·送人》一词，完成后面的题。
                                                                                                   鹧鸪天 送人
                                                                                                    辛弃疾
                                               唱彻《阳关》泪未干，功名馀是且加餐。浮天水送无穷数，带雨云埋一半山。
                                              今古恨，几千般，只应离合是悲欢？江头未是风波恶，别有人间行路难！

There ____ (be) few students playing in the playground because of the coming exam, will there?

已知复数$z=a+bi$($a,b\in R$且$ab$≠$0$)，且$z\left(1-2i\right)$为实数，则$\frac{a}{b}=$(      )