What is the simple interest rate for a fund that starts with $1,550 on July 15,a deposit of $730 37 days later, a withdrawal of $250 100 days later, and abalance of $2,211

Expert Answers
tjbrewer eNotes educator| Certified Educator

Simple interest is applied by `V=P+Prt` We find the combined value of the fund by breaking the values into simpler sets of computations. 

`V_1=1,550+1,550(37)(r)=1,550+57,350r` Is the value of the fund when the deposit was made.

`V_2=V_1+730` is the value of the fund after the deposit is made

After the fund completes its 100 day maturation, its value is the 2,211 in the account + the withdrawal of 250 for a final value of 2,461


We replace the values with their computed findings






`2,280+200,990r+3,613,050r^2=2,461` We solve for 0

`3,613,050r^2+200,990r-181` and apply the Quadratic Formula


That comes out to r=.0886%/day or 32% APR