GWD-2-28

knight9514

Q28:

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

A. 280

B. 400

C. 540

D. 600

E. 840

Ans: D

Please, help. I do unrealize! How to calculate? 

mikejia

hi, Man. without hatched, how comes "survive".

2. one egg birth one geese if it can be hatched.

[此贴子已经被作者于2006-8-4 21:54:54编辑过]

knight9514

謝謝牛人的精闢解答!

但對題意仍有2個疑問?

1."Of the geese survived the first month"

  = "有Hatched"且"survived the first month" + "沒有Hatched"且"survived the first year"

   (如果是這樣,後者沒有給條件,就求不出來!)

2."if no more than one goose hatched from each egg"是什麼意思?

  (是說"沒有Hatched"的部分嗎?)

幫忙解惑一下!   感謝牛人的幫忙!

叮叮当当

2/3*3/4*(1-2/5)=1/5  这个是第一年的存活率

所以总数为：120/(1/5)=600

mikejia

120/0.4/0.75/(2/3)=600