# Fight Finance

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In Australia in the 1980's, inflation was around 8% pa, and residential mortgage loan interest rates were around 14%.

In 2013, inflation was around 2.5% pa, and residential mortgage loan interest rates were around 4.5%.

If a person can afford constant mortgage loan payments of \$2,000 per month, how much more can they borrow when interest rates are 4.5% pa compared with 14.0% pa?

Give your answer as a proportional increase over the amount you could borrow when interest rates were high $(V_\text{high rates})$, so:

$$\text{Proportional increase} = \dfrac{V_\text{low rates}-V_\text{high rates}}{V_\text{high rates}}$$

Assume that:

• Interest rates are expected to be constant over the life of the loan.
• Loans are interest-only and have a life of 30 years.
• Mortgage loan payments are made every month in arrears and all interest rates are given as annualised percentage rates (APR's) compounding per month.