# UnitMath FAQ ( General )

### What is UnitMath? TOP

UnitMath is a calculation program that enables you to answer questions, when the questions can be written as equations involving units and numbers with precision ( uncertainty ).

For example:

The Question:
How many acres are in a field that measures 1.2 miles by 80 feet ± 1 foot?

1.2 mile * ( 80 feet ± 1 foot ) as acres ~ ( 11.01 to 12.27 ) acres

Details:
Looking at the length and width in detail yields:

Value Low High Units Comment
1.2 miles 1.15 1.25 miles 1.2 has 2 significant digits
80 feet ± 1 foot 79 81 feet pm can be used for ±

"*" means multiply by, so "length * width" means "length multiplied by width".

"as acres" tells UnitMath the units we want in the answer.

Putting this all together we get the following equation:
1.2 mile * ( 80 feet ± 1 foot ) as acres

When when evalueted the above equation returns:
~ ( 11.01 to 12.27 ) acres

As you can see the result is inexact and has the requested units. In general, if the input is inexact, the result is inexact.

### What can I do with UnitMath? TOP

Any of the following.

Arithmetic Calculations
1 + 20 + 300 + 4000 = 4,321
5 * 6 + 7 = 37
81/9 - 3 = 6

Conversions
ton as pound = 2,000 pound
mile as yard = 1,760 yard
hour as seconds = 3,600 seconds

Arithmetic Calculations with Units
ton - 100 pounds as pounds = 1,900 pounds
mile - 3000 feet as yards = 760 yards
hour - 360 seconds as minutes = 54 minutes

Use Prefixes and Units
kiloGram as grams = 1,000 grams
kiloMeter as feet ~ 3,281. feet
megaSeconds as days ~ 11.57 days

Use Precision with Numbers
1.0 ~ 0.95 to 1 to 1.05
2 pm 3 ~ -1 to 2 to 5
3 to 9 ~ 3 to 6 to 9
3 to 4 to 9 ~ 3 to 4 to 9

Use Precision with Units
1.0 ton as pounds ~ ( 1,900 to 2,000 to 2,100 ) pounds
2 yards pm 3 feet as feet ~ ( 3 to 6 to 9 ) feet
3 inches to 9 inches as inches ~ ( 3 to 6 to 9 ) inches
3 mile to 4 mile to 9 mile as miles ~ ( 3 to 4 to 9 ) miles

Use Functions
sin( pi / 2 ) = 1
cos( 0 deg ) = 1
tan( 86 deg pm 3.9 deg ) ~ 7.21 to 14.30 to 572.96

Use Variables
density: gram per cubic centimeter = kg/liter
5 gallon * density as pounds ~ 41.73 pounds
50 pounds / density as gallons ~ 5.99 gallons
density as pounds per gallon ~ 8.35 pounds per gallon

### What does ~ mean? TOP

There are four different ways UnitMath responds to a calculation:

If the result can be displayed exactly it's prefixed by =.
4/2 = 2
foot/inch = 12
inch as cm = 2.54 cm

If the result can NOT be displayed exactly it's prefixed by ~.
pi ~ 3.14159
21.3 centimeter as inch ~ 8.4 inch
68.2 degF as degC ~ 20.1 degC

If the calculation can't be completed the error is surrounded by *** ***.
foot as gallon *** Can't evaluate equations like: ft as gal ***
3.2e3.1 *** In exponents, 'e' must be followed by an integer ***
foot + second *** ( ft ) + ( s ) ***

When several variables are defined only the last result is displayed.
len: 50 feet; wid: 500 yard; len * wid as acres ~ 1.722 acres

### How do I do a calculation in UnitMath? TOP

Enter the Equation.

On any blank line in the UnitMath window, enter the equation you want to calculate. For example: 2 + 2 .

If needed, make a clear area by pressing the enter key several times, or deleting some existing text.

Mark the Equation(s) you want to evaluate.

There are two ways to do this:

Selection Method: Select ( highlight ) the equation 2 + 2.

Cursor Method: Put the insertion cursor is on the same line as 2 + 2, with nothing selected. The new result will automatically be overwrite the old displayed result.

Evaluate the Equation.

Tap the "=" button at the bottom of the "UnitMath" window or press the F12 key to start the calculation, and the result will be displayed: 2 + 2 = 4

### Why doesn't UnitMath have a File menu with a Save & Print options? TOP

UnitMath is intended as a worksheet to do calculations which are to be added to other documents that will include supporting text, tables, graphs and drawings. There are many great existing programs for word processing, drawing and presenting data. UnitMath is a powerful support tool to these existing programs. To use UnitMath with these programs simply copy and paste between UnitMath and the other program.