NO.PZ2018062002000051
问题如下：
Benedict, an analyst from an investment company, recently gathered the following data for an equal-weighted index comprised of securities G,H,I:
What is the index's return over the period?
选项：
A. 1.71%.
B. 6.83%.
C. 5.24%.
解释：
Equal-weighted index, the investment amount of each security in the index is the same.
Suppose each of these three stocks invests $1,050, the index’s beginning value is $3150, and the number of shares can be purchased for stock G is , for stock H is , for stock I is .Therefore, the end value of the index is $17×70+$33×30+$40×28.38=$3315.20
The price return is $3,315.20/$3,150 – 1 = 5.24%.
考点：等权重指数计算收益率
等权重有两种思路来计算，一种方式也是李老师上课讲的（直接计算收益率之和除以3）。还有一种就是这道题的思路，它是从等权重最本源的含义出发的：假设每只股票买相同的金额，因此每只股票在指数中的权重是相等的。两种方法的结果是一致的。但解析做法没有咱们上课讲的直接计算收益率之和除以3简便。
简单说一下，假设每只股票没相同的金额1050, 因此期初三只股票价值=1050*3=3150（这只是题目假设，可以是任意金额，10,100,1000都可以），那么期初G股票可以买1050/15=70只，H可以买30只，I可以买28.4只股票。到了期末由于三只股票价格发生变化，G价值=70*17=1190，H价值=30*33=990， I价值=28.4*40=1135.1，所以期末三只股票的价值=1190+990+1135.1=3315.1
因此该股指的收益率就等于期末价值除以期初价值减1= $3,315.20/$3,150 – 1 = 5.24%.
老师可以讲解更详细点吗？
