GWD-5-21

Theater M has 25 rows with 27 seats in each row.  How many of the seats were occupied during a certain show?

(1)   During the show, there was an average (arithmetic mean) of 10 unoccupied seats per row for the front 20 rows.

(2)   During the show, there was an average (arithmetic mean) of 20 unoccupied seats per row for the back 15 rows.

为什么不是选C呢，前十排坐27个，后面十五排都坐7个，这样不就可以得出答案了吗？

up

不是这个意思的。不是说有没有可能有解，而是是不是肯定有唯一解。

如果前15排，中间5排，后10排，坐的人分别是a,b,c，那么有(a+b)/20等于某值，(b+c)/15等于另一值，但是总数算不出来的吧。无穷多解。

Theater M has 25 rows with 27 seats in each row.  How many of the seats were occupied during a certain show?

(1)   During the show, there was an average (arithmetic mean) of 10 unoccupied seats per row for the front 20 rows.

(2)   During the show, there was an average (arithmetic mean) of 20 unoccupied seats per row for the back 15 rows.

为什么不是选C呢，前十排坐27个，后面十五排都坐7个，这样不就可以得出答案了吗？

豁然开朗，深夜做蒙了

THX！