For a recent play performance, the ticket prices were $25 per adult and $15 per child. A

total of 500 tickets were sold for the performance. How many of the tickets sold were for

adults?

(1) Revenue from ticket sales for this performance totaled $10,500.

(2) The average (arithmetic mean) price per ticket sold was $21.


偶選C﹐答案是D

設成人數量為A﹐兒童為C﹐

條件1的方程式是﹕25A+15C=10500 如何得知A是多少﹖

條件2的方程式﹕25A+15C/A+C=21 ﹐ 也無法單獨求出A是多少

真的8理解﹐請大家幫忙看看﹐謝謝