The [difference](https://artofproblemsolving.com/wiki/index.php/Subtraction) between a $6.5\%$ sales tax and a $6\%$ sales tax on an item priced at $$20$ before tax is
$\text{(A)}$ $$.01$
$\text{(B)}$ $$.10$
$\text{(C)}$ $$ .50$
$\text{(D)}$ $$ 1$
$\text{(E)}$ $$10$
The most straightforward method would be to calculate both prices, and subtract. But there's a better method...
Before we start, it's always good to convert the word problems into [expressions](https://artofproblemsolving.com/wiki/index.php/Expression), we can solve.
So we know that the price of the object after a $6.5\%$ increase will be $20 \times 6.5\%$, and the price of it after a $6\%$ increase will be $20 \times 6\%$. And what we're trying to find is $6.5\% \times 20 - 6\% \times 20$, and if you have at least a little experience in the field of [algebra](https://artofproblemsolving.com/wiki/index.php/Algebra), you'll notice that both of the items have a common [factor](https://artofproblemsolving.com/wiki/index.php/Divisor), $20$, and we can [factor](https://artofproblemsolving.com/wiki/index.php/Factoring) the expression into 
\begin{align*} (6.5\% - 6\% ) \times 20 &= (.5\% )\times 20 \\ &= \frac{.5}{100}\times 20 \\ &= \frac{1}{200}\times 20 \\ &= .10 \\ \end{align*}
$.10$ is choice $\boxed{\text{B}}$