Of the goose eggs laid at a certain pond, ~$2 \over 3$~ hatched, and ~$3 \over 4$~ of the geese that hatched from those eggs survived the first month. Of the geese that survived the first month, ~$3 \over 5$~ did not survive the first year. If 120 geese survived the first year and if no more than one goose hatched from each egg, how many goose eggs were laid at the pond?


280

400

540

600

840

考题讲解

题目分析:

假设G代表池塘里的鹅蛋数量,~$\frac{2}{3}$~G孵化,第一个月活下来的数量是  ~$\frac{3}{4}*\frac{2}{3}G=\frac{1}{2}G$~。第一年活下来的数

量就是(1-~$\frac{3}{5})*\frac{1}{2}G =\frac{1}{5}G$~; 因为第一年活下来的数量是120,所以,~$\frac{1}{5}G=120$~.解得G=600    

本题思路简单,只要细心的根据题目中的条件一个一个的算下来,就很容易得到答案。

综上:答案是 D。

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