盒子里有若干个相同的小球 ，甲取走一半后，乙又取各剩余的，丙再取走5个，这时，还剩下3个，则盒子里原有     个小球；

(－6≤a≤3)的最大值为   (　　)．

根据短文内容判断下列句子正误。
    My name is Amy. Tomorrow is Saturday. My parents aren't going to work, but we are going to be very busy tomorrow. My mother is going to buy something. I'm going to the bookstore in the morning. Then I'm going to buy a dictionary.
    Tomorrow evening we are going to visit my grandparents and have a big dinner. After that we are going to the cinema. I think we are going to have a nice weekend.

用化学用语填空：

如图甲所示电路，电源电压恒定，R₀为定值电阻，闭合开关S，当滑动变阻器的滑片P从一端移到另一端的过程中，电流表示数I与电压表示数U的关系如图乙所示，则定值电阻R₀的阻值为____Ω；当滑动变阻器接入电路阻值分别为 $\frac{1}{4}$ R和R时，电路消耗的总功率为P₁、P₂，则P₁：P₂=____。