Mathematics

Lengths - measured in metres and millimeters - there are 1000 millimetres in a metre

Depths - measured in metres and decimal fractions - eg 1.25 metres deep

Areas - measured in square metres ( m2 )

Volumes - measured in cubic centimeters, litres and cubic metres. - there are 1000 cubic centimeters in a litre and 1000 litres in a cubic metre.

Weights - measured in grams and kilograms and tonnes - there are 1000 grams in a kilogram and 1000 kilograms in a tonne.

Percentages - the number of units measured divided by 100 of those units

1 percent written as 1% is the same as 1/100

15 percent written as 15 % is the same as 15/100

Decimals

• 10 is what you get when 1 is multiplied by 10 - it can also be called 10 to the power of 1
• 100 is what you get when 1 is multiplied by 100 - it can also be called 10 to the power of 2
• 1000 is what you get when 1 is multiplied by 1000 - it can also be called 10 to the power of 3
• 0.100 is what you get when 1 is divided by 10 - it can also be called 10 to the power of minus 1
• 0.010 is what you get when 1 is divided by 100 - it can also be called 10 to the power of minus 2
• 0.001 is what you get when 1 is divided by 1000 - it can also be called 10 to the power of minus 3

Many results of testing water used in aquaculture use measurements like parts per million ( PPM ) or milligrams per litre ( mg/l )

A milligram is a thousandth of a gram ( 1/1000 gm ) so one milligram in one litre of water is 1 unit in 1/1000 x 1000 which is 1/1,000,000 - one part in one million parts

A molar solution of a substance is one molecule of the substance in one litre of water with the molecule being the sum of the atomic masses in grams. A molecule of salt is NaCl ( one sodium atom joined to one chloride atom ) So a molar solution of salt would be the atomic mass of sodium ( Na ) 23 plus atomic mass of chloride ( Cl ) 35.5 which equals 58.5 grams of salt dissolved in one litre of pure water.

A millimole solution would be a molar solution divided by 1000