## Getting to know

# Magic Number

# I only have one minute…

This video gives you a quick overview.

# I like to know more…

We can tell you the features. But this is only half the story.

The other half is how easy or how well it performs.

We will show you ways to do math with less effort.

So you get a sense of “how” as well as a taste of the UI.

Let’s begin.

# Do math with less effort

# Make yourself comfortable

Magic Number is not a physical calculator. You can have it any size.

And feel free to go buttonless.

But before you hide the buttons…

# Keypad for learning.

The keypad is really for helping you to get familiar with the app, and in particular, the shortcut.

As you have expected, every button has a shortcut.

In fact, you can do everything without touching the mouse.

(Look under Help for a full list of shortcuts.)

# Editing at its simplest

You can click and type.

Or use the keys `◀`,`▶`

Of course you can go further.

# You can’t go fast with square wheels.

The QWERTY keyboard is never meant for math.

Math symbols are second class citizens.

To multiply, you have to hunt for `*`

To add, you have to press shift with

Of course there is a better way — you can cure this in seconds.

# Faster switching.

If you switch between a calculator and another app a lot, treat yourself with the global shortcut *⌃space*. You can use it in any app.

Press it to show Magic Number. And when you’re done, press again to hide it.

## Do more for less while switching

Sometimes you want to calculate, copy the result, and switch back.

You can let Magic Number do the copying for you.

# R is for result.

For safety, the result of your most recent calculation is automatically saved. You can access it by clicking

or by pressing R.It’s convenient for calculation too.

Let’s say I’m calculating my total journey time:

My distance is 15 km. To calculate the speed, I can simply enter

15 ÷

This means you have less things to worry about:

- No need to copy the result beforehand.
- No need to discipline yourself to store 1:15 as a variable.
- No need to use the prehistoric M+, MR, etc.

# List – A mini spreadsheet

Get the sum, tax, and statistics for a list of numbers.

Click the below image for a quick demo.

## Comparing numbers

Here are some prices for the Apple Watch.

Watch Sport | 38mm | $349 |

Watch Sport | 42mm | $399 |

Watch | 38mm | $549 |

Watch | 42mm | $599 |

Let’s compare the 38mm models.

### Difference (549 – 349)

### % increase (349 ➝ 549)

(Conclusion: My brain thinks the Sport is better. But my heart disagrees.)

# History – Exploit the past

You can *double-click* to insert your past calculation —

whether it’s for correction or for doing a similar calculation.

*Select something* to see the sum, average, or other summary.

So instead of typing one long expression, e.g. ‘(349 + 649) + (80 – 25%)’,

you can combine shorter ones.

# Embrace the unknown

Magic Number can do algebra for you. For example:

*Something* ÷ 17 = 19

*Something* is the unknown. Similar to ‘x’ in elementary algebra.

Enter:

÷ 17 = 19

You get:

Let’s solve another problem.

## Aspect ratio problem

Example:

HD video has width-to-height ratio 16:9. If the width is 800, what is the height?

In other words…

As ratio is analogous to division…

Enter *16 ÷ 9 = 800 ÷ ?*, you get:

*Hint:* You formulate by aligning related quantities.

(You get the same result with ? ÷ 800 = 9 ÷ 16.)

To learn more about the unknown, click here.

# Compound interest — The lazy way

Let’s start with *simple* interest.

If we borrow $ *2000* with *10*% interest, we will pay back:

For convenience, we type:

If the interest is *compounded* yearly for *3* years, our payment is:

We can simply type:

You can read it as ‘2000 with 10% compounded 3 times’.

Here’s the answer.

## Let’s play a bit of what-if’s.

What if we want 3000 instead of 2662? What rate would that be?

The best rate we can get is 12%. How many years it takes to reach 3000?

I hope you find this easier than the normal math or the spreadsheet’s future value function. You can learn more about compounding here.

# Need to know more?

The home page shows you more details and screenshots.

If you have any questions, feel free to tweet me.

Oh my name is Dennis Liu and I am the developer of Magic Number.

Have a nice day.