A grocer stacked oranges in a pile. The bottom layer was rectangular with 3 rows of 5 oranges each. In the second layer from the bottom, each orange rested on 4 oranges from the bottom layer, and in the third layer, each orange rested on 4 oranges from the second layer. Which of the following is the maximum number of oranges that could have been in the third layer?
5
4
3
2
1
每层之间的关系是,每上升一层,横排减一,纵排减一;
从最底层开始 A*B个,那么上面一层就是(A-1)*(B-1)个。
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