Independent solution

How to solve this Arithmetically Increasing Perpetuities question

Setup

Setup

Separate the half-year and year-end payments into two annual sequences. Each sequence begins at 500 and increases by 10 each year.

i=0.075i=0.075
j=(1.075)1/21=0.0368221j=(1.075)^{1/2}-1=0.0368221

Model

Model

An annual perpetuity with first payment P at time 1 and annual increase Q has value P divided by i plus Q divided by i squared. The half-year sequence is shifted six months earlier.

PVyear=5000.075+100.0752PV_{\mathrm{year}}=\frac{500}{0.075}+\frac{10}{0.075^2}
PVhalf=(1.075)1/2PVyearPV_{\mathrm{half}}=(1.075)^{1/2}PV_{\mathrm{year}}

Compute

Compute

The year-end sequence is worth 8,444.44, and shifting the other sequence earlier raises its value to 8,755.39.

PVyear=8444.44PV_{\mathrm{year}}=8444.44
PVhalf=8755.39PV_{\mathrm{half}}=8755.39
PV=17199.83PV=17199.83

Answer

Answer

The required fund is about 17,200, which is choice E.

PV17200(E)\boxed{PV\approx17200\quad\text{(E)}}