Original practice · fully worked
Original variant: opening credit balance from mid-month charges and month-end payments
A credit account earns 12% annual effective interest. During each of six months, 50 is charged at mid-month and 200 is paid at month-end. Immediately after the sixth payment, the balance is 500. Calculate the balance immediately before the first mid-month charge.
- A
1,140.64 - B
1,207.74 - C
1,274.84 - D
1,341.93 - E
1,409.03
Answer and calculation
Discounting six payments and the ending balance, then subtracting the six mid-month charge values, gives opening balance 1,341.93, choice D.
Setup
Setup
Use the monthly accumulation factor equivalent to 12% annual effective.
q=(1.12)1/12 Model
Model
At time 0, opening balance plus charge present values equals payment present values plus the terminal balance present value.
X+n=1∑650q−(n−0.5)=n=1∑6200q−n+500q−6 Compute
Compute
Solving the present-value equation gives X = 1341.93.
X=1341.93239120 Answer
Answer
The opening balance is 1,341.93, selecting choice D.
X≈1341.93(D)