Appendix 1: AV Maths

Question 1

What is the correct order of operations when solving a formula?

Answer 1

BODMAS 
Brackets
Orders 
Division 
Multiplication 
Addition
Subtraction

(Some mnemonics might use Parentheses instead of Brackets and Exponents instead of Orders)

Question 2

How is Aspect Ratio calculated?

Answer 2

Aspect Ratio

AR = W/H

Screen width divided by height.

Question 3

What mathematical formula can be used to calculate diagonal screen size?

Answer 3

Pythagoras

The square of the diagonal is equal to the squares of the wide and height added together.

Question 4

How do you estimate the distance to place a projector?

Answer 4

Distance =

Screen Width x Throw Ratio

Question 5

How do you calculate required screen and viewing distance?

Answer 5

Screen Height
= Max Distance / N

N will vary depending on the task:
8 for general viewing, videos etc
6 for reading, e.g. presentations
4 for detailed inspection

For a given screen height you can calculate max distance using
D = H x N

Question 6

How do you calculate Max Distance from Text Height?

Answer 6

Max Distance = Text Height x 150

Question 7

What is Ohm’s Law for Current?

Answer 7

V = I x R

Voltage = Current x Resistance

Question 8

How do you calculate Heat Load?

Answer 8

Apart from amplifiers, 1 watt of power produces 3.4 Btu of heat.