This Exam FM sample reference tests Deposits Accumulated into a Semiannual Perpetuity. Accumulating the five beginning-year deposits to year 10 gives 1703.81. The half-year rate equivalent to 12% annually is 5.8301%, so the perpetuity-immediate payment is 99.33, choice A.
These notes identify the calculation error associated with each wrong letter when that error is reproducible.
BChoice B divides 12% by two instead of using the exact half-year rate equivalent to 12% effective.
CChoice C delays all deposits by one year before accumulating them.
DChoice D uses 12% as the half-year perpetuity rate.
EChoice E treats the perpetuity as due and then doubles its semiannual payment.
Original practice · fully worked
Original variant: scale deposits to buy a target perpetuity
Deposits of 100q, 150q, and 200q are made at times 0, 1, and 2 into a fund earning 8% annually. At time 6 the fund buys a perpetuity-immediate paying 120 every half-year, valued at a 10% annual effective yield. Determine q.
A 3.20
B 3.48
C 3.78
D 4.05
E 4.32
Variant answer in brief
The perpetuity requires 2458.57 at time 6, while the unscaled deposits accumulate to 651.18. Their ratio is q = 3.7755, choice C.
Setup
Setup
Find the half-year rate and the fund required for the perpetuity.
j=(1.10)1/2−1
F6=j120=2,458.5706
Model
Model
Accumulate one unit of the stated deposit pattern to time 6.
B=100(1.08)6+150(1.08)5+200(1.08)4=651.1844
Compute
Compute
The actual accumulated deposits equal q times this base value.
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