课件中给出的公式是这样的：
和题目的解释不一样，求解！！！！
100. A bond with a par value of $100 matures in 10 years with a coupon of 4.5%, paid semiannually; is priced to yield 5.83%; and has a modified duration of 7.81. If the yield of the bond declines by 0.25%, the approximate percentage price change for the bond is closest to:
A. 0.98%.
B. 1.95%.
C. 3.91%.
B is correct. Approximate percentage price change = –(7.81 × (–0.0025)) = 0.01953 or 1.95%.
为什么这题没有考虑convexity的影响？
103. The duration and convexity of an option-free bond priced at $90.25 are 10.34 and 75.80, respectively. If yields increase by 200 basis points, the percentage change of the price is closest to:
A. –23.71%.
B. –20.68%.
C. –17.65%.
C is correct; the percentage change in price is calculated as follows: Duration effect:－10.34* (＋0.02 )=－20.68% and convexity effect: 75.80*(0.02 ) 平方＝3.03%. Total percentage change is the sum of duration effect and convexity effect: －20.68％＋3.03%＝－17.65%.
和课件中的公式不一致，上课何老师还特意强调要＊0.5的