为什么IM是50%？

NO.PZ2015122802000023问题如下The current priof a stois $25 per share. You have $10,000 to invest. You borrow aition$10,000 from your broker aninvest $20,000 in the stock. If the maintenanmargin is 30 percent, whpriwill a margin call first occur?A.$9.62.B.$17.86.C.$19.71. is correct.A margin call will first occur a priof $17.86. Because you have contributehalf anborrowethe remaining half, your initiequity is 50 percent of the initistoprice, or $12.50 = 0.50 × $25. If P is the subsequent price, your equity woulchange amount equto the change in price. So, your equity priP woul12.50 + (P – 25). A margin call will occur when the percentage margin ops to 30 percent. So, the priwhia margin call will occur is the solution to the following equation.Equity/SharePrice/Share=12.50+P−25P=30%\frac{Equity/Share}{Price/Share}=\frac{12.50+P-25}P=30\%Price/ShareEquity/Share​=P12.50+P−25​=30%The solution is P = $17.86.考点LeveragePosition这道题目，解题方法有两种方法一期初股价25元，我们借钱买股票，所以自有资金是12.5，自有资金占股价比例12.5/25=50%。当股价从25元跌到P,那么自有资金就跟着减少，当自有资金比例减少到30%时[12.5-（25-P）]/P=30%,低于这个P我们就要接到电话了。计算得到P=17.86方法二直接根据公式，PL=P0*（1-IM）/(1-MM)=25*(1-50%)/(1-30%)=17.86 我自己想不出来，怎么算都有问题

NO.PZ2015122802000023 问题如下 The current priof a stois $25 per share. You have $10,000 to invest. You borrow aition$10,000 from your broker aninvest $20,000 in the stock. If the maintenanmargin is 30 percent, whpriwill a margin call first occur? A.$9.62. B.$17.86. C.$19.71. is correct.A margin call will first occur a priof $17.86. Because you have contributehalf anborrowethe remaining half, your initiequity is 50 percent of the initistoprice, or $12.50 = 0.50 × $25. If P is the subsequent price, your equity woulchange amount equto the change in price. So, your equity priP woul12.50 + (P – 25). A margin call will occur when the percentage margin ops to 30 percent. So, the priwhia margin call will occur is the solution to the following equation.Equity/SharePrice/Share=12.50+P−25P=30%\frac{Equity/Share}{Price/Share}=\frac{12.50+P-25}P=30\%Price/ShareEquity/Share​=P12.50+P−25​=30%The solution is P = $17.86.考点LeveragePosition这道题目，解题方法有两种方法一期初股价25元，我们借钱买股票，所以自有资金是12.5，自有资金占股价比例12.5/25=50%。当股价从25元跌到P,那么自有资金就跟着减少，当自有资金比例减少到30%时[12.5-（25-P）]/P=30%,低于这个P我们就要接到电话了。计算得到P=17.86方法二直接根据公式，PL=P0*（1-IM）/(1-MM)=25*(1-50%)/(1-30%)=17.86 不太能理解自有资金是12.5？自有资金不是10000吗？12.5应该是用来形容股价的

NO.PZ2015122802000023 问题如下 The current priof a stois $25 per share. You have $10,000 to invest. You borrow aition$10,000 from your broker aninvest $20,000 in the stock. If the maintenanmargin is 30 percent, whpriwill a margin call first occur? A.$9.62. B.$17.86. C.$19.71. is correct.A margin call will first occur a priof $17.86. Because you have contributehalf anborrowethe remaining half, your initiequity is 50 percent of the initistoprice, or $12.50 = 0.50 × $25. If P is the subsequent price, your equity woulchange amount equto the change in price. So, your equity priP woul12.50 + (P – 25). A margin call will occur when the percentage margin ops to 30 percent. So, the priwhia margin call will occur is the solution to the following equation.Equity/SharePrice/Share=12.50+P−25P=30%\frac{Equity/Share}{Price/Share}=\frac{12.50+P-25}P=30\%Price/ShareEquity/Share​=P12.50+P−25​=30%The solution is P = $17.86.考点LeveragePosition这道题目，解题方法有两种方法一期初股价25元，我们借钱买股票，所以自有资金是12.5，自有资金占股价比例12.5/25=50%。当股价从25元跌到P,那么自有资金就跟着减少，当自有资金比例减少到30%时[12.5-（25-P）]/P=30%,低于这个P我们就要接到电话了。计算得到P=17.86方法二直接根据公式，PL=P0*（1-IM）/(1-MM)=25*(1-50%)/(1-30%)=17.86 老师这道题初始保证金是50%，即自有资金10000元为保证金；题目中降到30%时即到维持保证金，即自有金额降到6000元，那么自有资金减少了4000元时候，需要受到margincall。那为什么思路不能是4000除以（20000/25）=5元时，即每股亏损5块钱时受到margin call这个思路来算呢？

NO.PZ2015122802000023问题如下 The current priof a stois $25 per share. You have $10,000 to invest. You borrow aition$10,000 from your broker aninvest $20,000 in the stock. If the maintenanmargin is 30 percent, whpriwill a margin call first occur?A.$9.62.B.$17.86.C.$19.71. is correct.A margin call will first occur a priof $17.86. Because you have contributehalf anborrowethe remaining half, your initiequity is 50 percent of the initistoprice, or $12.50 = 0.50 × $25. If P is the subsequent price, your equity woulchange amount equto the change in price. So, your equity priP woul12.50 + (P – 25). A margin call will occur when the percentage margin ops to 30 percent. So, the priwhia margin call will occur is the solution to the following equation.Equity/SharePrice/Share=12.50+P−25P=30%\frac{Equity/Share}{Price/Share}=\frac{12.50+P-25}P=30\%Price/ShareEquity/Share​=P12.50+P−25​=30%The solution is P = $17.86.考点LeveragePosition这道题目，解题方法有两种方法一期初股价25元，我们借钱买股票，所以自有资金是12.5，自有资金占股价比例12.5/25=50%。当股价从25元跌到P,那么自有资金就跟着减少，当自有资金比例减少到30%时[12.5-（25-P）]/P=30%,低于这个P我们就要接到电话了。计算得到P=17.86方法二直接根据公式，PL=P0*（1-IM）/(1-MM)=25*(1-50%)/(1-30%)=17.86 分母没有争议，就是现在股价。分子的话，之前一直没想通的一点是，既然自有资金和借的钱都投进去了，干嘛只减自有资金。其实你借的钱赚了亏了都不变，你还是要还1w。变得只有你自有资金一万。所以自有资金比例，即分子就是初始自有资金 - 亏损的钱（也就是股价下跌）。所以分子就是12.5-（25-现在股价）。我觉得我悟了。