# Calculating percents with “-” sign?

For example yesterday I had 886 dollars. But today I have only 877 dollars. How can I calculate how much richer am I today than yesterday in percents ( so number of percents should be with "-" ).

How can I calculate it?

I have to do this in many ways, but unfortunately i can't get the right result.

Thanks.

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Have you tried ${t\over y}-1$? $t$ is today, $y$ is yesterday. – abiessu Sep 27 '13 at 16:44
No offense ... but by your given amounts, you're becoming poorer not richer than yesterday – user67258 Sep 27 '13 at 16:58
so number of percents should be with "-" (from my question) – Mike Vayvala Sep 27 '13 at 17:59

Let $x_0$ be your initial amount of money, and $x_1$ be your new amount. The percent increase is calculated as follows:
$$\frac{x_1-x_0}{x_0}\cdot{100\%}$$