Exact Simple Interest Problem Determine the **exact** simple interest on **1,000,000** invested for the period from **October 24,1987 to January 7, 1990** ; if the rate of interest is **17%**. What I've tried: October 24, 1987 to October 24, 1988 -> 365 days October 24, 1998 to October 24, 1989 -> 365 days October 24, 19 1989 to January 7, 1990 -> 75 days I = Pin = $(1,000,000)(\frac{0.17}{365})(365 + 365 + 365) = 374,931.51$ But the answer should be: **93,785.079.** Any ideas what I got wrong? Thank you~

Your answer is correct.

$$\mbox{October } 24-31 \mbox{ is } 7 \mbox{ days}\ \ \ \ \ \ \ \ \ \ \ \ \ \mbox{Total days in }1987 \mbox{ is }68 \mbox{ days} $$

$$\mbox{November } 30 \mbox{ days}\ \ \ \ \ \ \ \ \ \ \ \ \ \mbox{Total days in }1988 \mbox{ is }366 \mbox{ days} $$

$$\mbox{December } 31 \mbox{ days}\ \ \ \ \ \ \ \ \ \ \ \ \ \mbox{Total days in }1989 \mbox{ is }365 \mbox{ days} $$

$$\mbox{October } 1-7 \mbox{ is } 7 \mbox{ days}\ \ \ \ \ \ \ \ \ \ \ \ \ \mbox{Total days in }1990 \mbox{ is }7 \mbox{ days} $$

So, Number of interest days $=68+366+365=806$

Number of days from $1987$ to $1990$ is $=365+366+365+365=1461$

So, $I=1,000,000(0.17)\left(\dfrac{806}{1461}\right)=93,785.079$