Math CentralQuandaries & Queries


Question from John:

I was wonder how to find the Original cost when you don't know original cost

The amount paid was 13.82 that is suppose to represent 20% because Insurance pays 80%

Thank You

Hi John,

I can show you a couple of ways to approach this problem.

First approach:

The numbers here make the arithmetic straightforward. Since 80 is 4 times 20 and the amount paid was 13.82, the insurance paid $4 \times 13.2$ and the original cost is the sum of what you paid and what the insurance paid. Even if the numbers were not so nice, suppose you paid 18% and the insurance company 82% then the insurance company would pay $\large \frac{82}{18} \normalsize \times 13.892.$

Second approach:

Suppose that the original cost was $x$ then 13.82 is 20% of $x,$ and hence $0.20 \times x = 13.2.$ Dividing both sides by 20 you get that $x = \large \frac{13.82}{0.20}.$

Solve the problem both ways to check your arithmetic.


About Math Central
* Registered trade mark of Imperial Oil Limited. Used under license.


Math Central is supported by the University of Regina and the Imperial Oil Foundation.
Quandaries & Queries page Home page University of Regina Imperial Oil Foundation