NO.PZ2018062002000020
问题如下：
Tim, an trader of an investment company trade on margin at a price of $60 per share, he purchased 300 shares of a non-dividend-paying stocks. The leverage ratio is 3. After three monthes the market price of share is $65, Tim then sells these shares. We assume that there are no transaction costs and no interests paid on the borrowed amount. Which of the following statements is correct?
选项：
A.The return to Tim during the three-month period was 20%.
B.The return to Tim during the three-month period was 8.33%.
C.The return to Tim during the three-month period was 25%.
解释：
C is correct.
The equity contributed by Tim (the minimum margin requirement) is \(\frac{100\%}3=33.33\%\)
Tim contributed 33.33% of $60 per share is $20.
The return is \(\frac{\$5}{\$20}=25\%\), because the gain is 5 ($65-$60) per share
考点：Leveraged Position
交易员借前买了300股，买的时候价格60每股，杠杆比率3。三个月后卖出时每股65元，让你计算3个月的收益。
杠杆比率等于A/E, 也就是购买一股股票需要花的钱除以每一股你自己出的钱=3。题目已知每股60元，那么A=60，因此每一只股票你自己只出了60/3=20。3个月股票以65元卖出，所以每一股收益等于65-60=5, 因此这笔交易你所获得的收益率（收益率就等于你赚的钱除以你自己投的钱）就等于5/20=25%。
此外，有四个小点需要注意：
1、只要题目出现（on margin or trade on margin or buy on margin）就是指保证金交易即借前买股票。
2、注意IM和MM的公式都是E/A，只不过是不同时点上的E和A。这道题里我们用杠杆反求出来的是初始保证金。
3、在一级权益里杠杆比率就是A/E , 可能其他学科还有自己的定义比如（D/E等），每个学科的知识点请按照每个学科具体规定来。
4、计算三个月的收益率不需要年化。一级权益这里一般不涉及年化问题。
请问我为什么不能用1/3相当于E/A margin的占比，然后再用600股乘以每股的价钱再乘以自己出钱的占比，这样一套算下来为什么答案还是错的
