①飘来飘去:____来____去;____来____去
②快快乐乐:____、____
③碧绿碧绿:____、____
④一朵朵:____、____
P(u﹣σ<X≤u+σ)=0.6826,
P(u﹣2σ<X≤u+2σ)=0.9544
P(u﹣3σ<X≤u+3σ)=0.9974,
一班有60名同学,一次数学考试的成绩服从正态分布,平均分110,方差为100,理论上说在120分到130分之间的人数约为( )
The rabbit has two ____(long; short) ears.