Question

:把1到15的15个自然数分成a,b两组.若把10从a转到b两组数平均值减1

Answer 1

设A组有x个数据,平均数为a,则B组有15-x个数据,平均数为b,可得：

ax+b(15-x)=120 ····························1

(ax-10)/(x-1)=a-1/2化简得：a=10.5-0.5x························2

[b(15-x)+10)/(15-x+1)=b-1/2·化简得：b=18-0.5x·········3

联立1、2、3式解得：

x=10

a=5.5

b=13