今天做ASM study manual FM 的题目如下: Jason deposits 3960 into a bank account at t = 0. The bank credits interest at the end of each year at a force of interest (delta) = 1/(8+t). Interest can be reinvested at an annual effective rate of 7%. The total accumulated amount at time t = 3 is equal to X. Caculate X. (A) 5394 (B) 5465 (C) 5551 (D) 5600 (E) 5685 答案是(A),解答如下: a(t) = (8+t)/8 i[t] = [a(t)/a(t-1)] -1 = 1/(7+t) Interest earned each year: 3960*i[1] = 3960*(1/8) = 495 3960*i[2] = 3960*(1/9) = 440 3960*i[3] = 3960*(1/10) = 396 AV = 3960 + 495(1.07)^2 + 440(1.07) + 396 = 5393.53 原本的想法是觉得因为 a(t) = (8+t)/8 = 1 + t/8 所以就把他当成是 simple interest 的给息方式 ( i = 1/8 ) 因此每年的 interest earned 都是 3960*(1/8) = 495 AV = 3960 + 495*(s3 angle 0.07) = 5551.37 刚好答案(C)也有这个数字... 想请问一下,这样的想法是不是哪边有错误? 若是往后又遇到 a(t) 的形式是 simple interest 的样子, 能够把他当成 simple interest 下去做吗? 谢谢!