答:设五个数为x1,x2,x3,x4,x5,依题意得
x1+x2+x3+x4+x5=5x102=510 (1)
x1+x2+x3=210 (2)
x3+x4+x5=390 (3)
(1)-(2) 得 x4+x5=300 (4)
(3)-(4)得x3=90
所以,中间数为90
答:设五个数为x1,x2,x3,x4,x5,依题意得
x1+x2+x3+x4+x5=5x102=510 (1)
x1+x2+x3=210 (2)
x3+x4+x5=390 (3)
(1)-(2) 得 x4+x5=300 (4)
(3)-(4)得x3=90
所以,中间数为90