Update README.md

README.md

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 |[A Concrete Introduction to Probability](ipynb/Probability.ipynb)&nbsp; &nbsp; **[NB](http:/nbviewer.jupyter.org/github/norvig/pytudes/blob/master/ipynb/Probability.ipynb)**, **[DN](https://beta.deepnote.org/launch?template=python_3.6&url=https%3A%2F%2Fgithub.com%2Fnorvig%2Fpytudes%2Fblob%2Fmaster%2Fipynb%2FProbability.ipynb)**<br>*Code and examples of the basic principles of Probability Theory.*|
 |[Probability, Paradox, and the Reasonable Person Principle](ipynb/ProbabilityParadox.ipynb)&nbsp; &nbsp; **[NB](http:/nbviewer.jupyter.org/github/norvig/pytudes/blob/master/ipynb/ProbabilityParadox.ipynb)**, **[DN](https://beta.deepnote.org/launch?template=python_3.6&url=https%3A%2F%2Fgithub.com%2Fnorvig%2Fpytudes%2Fblob%2Fmaster%2Fipynb%2FProbabilityParadox.ipynb)**<br>*Some classic paradoxes in Probability Theory, and how to think about disagreements.*|
+|[Estimating Probabilities with Simulations](ipynb/ProbabilitySimulation.ipynb)&nbsp; &nbsp; **[NB](http:/nbviewer.jupyter.org/github/norvig/pytudes/blob/master/ipynb/ProbabilitySimulation.ipynb)**, **[DN](https://beta.deepnote.org/launch?template=python_3.6&url=https%3A%2F%2Fgithub.com%2Fnorvig%2Fpytudes%2Fblob%2Fmaster%2Fipynb%2FProbabilitySimulation.ipynb)**<br>*When the sample space is too complex, simulations can estimate probabilities.*|
 |[Symbolic Algebra, Simplification, and Differentiation](ipynb/Differentiation.ipynb)&nbsp; &nbsp; **[NB](http:/nbviewer.jupyter.org/github/norvig/pytudes/blob/master/ipynb/Differentiation.ipynb)**, **[DN](https://beta.deepnote.org/launch?template=python_3.6&url=https%3A%2F%2Fgithub.com%2Fnorvig%2Fpytudes%2Fblob%2Fmaster%2Fipynb%2FDifferentiation.ipynb)**<br>*A computer algebra system that  manipulates expressions, including symbolic differentiation.*|
 |[Economics Simulation](ipynb/Economics.ipynb)&nbsp; &nbsp; **[NB](http:/nbviewer.jupyter.org/github/norvig/pytudes/blob/master/ipynb/Economics.ipynb)**, **[DN](https://beta.deepnote.org/launch?template=python_3.6&url=https%3A%2F%2Fgithub.com%2Fnorvig%2Fpytudes%2Fblob%2Fmaster%2Fipynb%2FEconomics.ipynb)**<br>*A simulation of a simple economic game.*|
 |[How to Count Things](ipynb/How%20To%20Count%20Things.ipynb)&nbsp; &nbsp; **[NB](http:/nbviewer.jupyter.org/github/norvig/pytudes/blob/master/ipynb/How%20To%20Count%20Things.ipynb)**, **[DN](https://beta.deepnote.org/launch?template=python_3.6&url=https%3A%2F%2Fgithub.com%2Fnorvig%2Fpytudes%2Fblob%2Fmaster%2Fipynb%2FHow%2520To%2520Count%2520Things.ipynb)**<br>*Combinatorial math: how to count how many things there are, when there are a lot of them.*|