http://www.analystforum.com/phorums/read.php?11,707293 Read the above post. Then my formula is as such (no need to remember much, except for your basic elementary algebra) a) Find the loan amount b) divide the loan amount by what % it represents of margin maintanence c) divide b by quanity of shares and the price you get will be the answer. so in reference to the post problem 1: 1300 = 75%, hence 1% = 1733, divide by shares 100 = 17.33 problem 2: 12000 = 75% hence 1% = 16000 divide by shares 200 = 80 Wow. donâ€™t know why book confuse us so much wrt to formulas.