Original practice · fully worked
Original variant: solve the first payment of an increasing annuity
An annuity-due makes 24 quarterly payments. Payment k, numbered from zero, is P plus 10k. Interest is a nominal annual rate of 6% compounded monthly. The annuity's present value is 6,000. Determine P.
- A
172.43 - B
181.25 - C
187.51 - D
197.51 - E
230.00
Answer and calculation
The equivalent quarterly rate is 1.5075125%. Separating the level and gradient present values and solving the linear equation gives P = 187.51, choice C.
Setup
Setup
Convert three monthly compounding periods into one quarterly effective rate.
jq=(1+0.06/12)3−1=0.015075125 Model
Model
Separate the unknown level payment from the known increase by quarter.
6,000=Pa¨24∣jq+10k=0∑23kvqk Compute
Compute
The due factor is 20.314637 and the gradient sum is 219.084828.
P=20.3146376,000−10(219.084828)=187.5077 Answer
Answer
The first payment is 187.51, choice C.
P=187.51(C)