A stock loses $10\%$ of its value on Monday.  On Tuesday it loses  $20\%$ of the value it had at the end of the day on Monday.  What is  the overall percent loss in value from the beginning of Monday to  the end of Tuesday?  Enter the answer as a percent.
If its initial value was $x$, after Monday, its value is $.9x$, and after a further $20\%$ loss, its value becomes $.8\cdot .9x = .72x$, making for a total loss of $\boxed{28\%}$.