gwd-21-4 谁帮忙翻译一下?顺便解一下

jerray

A total of 20 amounts are entered on a spreadsheet that has 5 rows and 4 columns; each of the 20 positions in the spreadsheet contains one amount.  The average (arithmetic mean) of the amounts in row i is R_i (1 ≤ i ≤ 5).  The average of the amounts in column j is C_j (1 ≤ j ≤ 4).  What is the average of all 20 amounts on the spreadsheet?

(1)     R₁ + R₂ + R₃ + R₄ + R₅ = 550

(2)     C₁ + C₂ + C₃ + C₄ = 440

jerray

忽然开窍,怎么刚才没读明白呢?大家见笑了!