## How Do You Do Permutations and Combinations in Desmos?

If you do not have a calculator that does combinations or permutations, there is another option to do those calculation. Desmos is know for its ability to graph formulas…but did you know it can also do calculations like a scientific calculator?

To find this scientific calculator, go to the Desmos website (www.desmos.com).

Located in the bottom left corner of the screen is a button to access the scientific calculator.Pressing this button takes you to the calculator. To access the command for permutations, press the button for func highlighted below.

This will take you to a new set of buttons. Select the button nPr shown below.

Pressing this button will paste the permutation command to the line above the buttons.

If you are computing 6P4 (or P(6,4)), you need to use your keyboard to type 6,4).

You can also do combinations in a similar manner.

If you type the carriage return on the keypad (dark blue button on the bottom right), it will go to a line on which you can put a new command.

To do a factorial like 10!, type in the number 10 on the keyboard.

Then select the ! button.

Notice that there are also other buttons that might prove useful like a square root, nth root, natural logarithm, and common logarithm buttons.

## The Compound Interest Formula and Its Many Faces

The compound interest formula appears in many classes. It can be confusing to students when it appears in one class as

and in another as

These are basically the same formulas, but used in a different context. However, how you solve for the different quantities in either one is the same. The Math-FAQs below demonstrate how to solve forĀ

## How Do I Use the Doubling Time to Find the Rate?

This week you will be graphing the function from Project 3. To find the equation for this function, you need to utilize the initial population and doubling time of the population. The goal of this post is to help you to find the rate r in the function $A(t)=P{{e}^{rt}}$. You will need to use the doubling time assigned to you in the project letter to do this.
Continue reading “How Do I Use the Doubling Time to Find the Rate?”