Trade Math
To convert from one unit to another within the metric system usually means moving a decimal point. If you can remember what the prefixes mean, you can convert within the metric system relatively easily by simply multiplying or dividing the number by the value of the prefix.
The most common metric measurements used in the food service industry are kilograms, grams, litres, and millilitres.
Example 1
Convert 26.75 kg to g.
First, write the question with the meaning of the prefix inserted. In this example, kis the prefix, andk means 1000, so:
26.75 kg = 26.75 × (1000) g = 26 750 g
Notice that there is no comma used in the answer 26 750 g. In the metric system, large numbers are separated every three digits by a space, not a comma.
Example 2
Convert 0.2 L to mL.
Again, write the question with the meaning of the prefix inserted. In this example, m is the prefix, and m means 0.001, so:
0.2 L = _____ (0.001) L
To find the blank (the value of the millilitres), divide the left-hand number by the right-hand number.
0.2 L ÷ 0.001 L = 200
This means 0.2 L = 200 mL.
Notice that there is a zero (0) before (to the left of) the decimal point. When writing decimal numbers that are smaller than 1 in the metric system, it is customary to place a zero to the left of the decimal point. Thus .6 in the metric system is written 0.6.
If you are working with two prefixes, you can convert in much the same way as above.
Example 3
Find the number of dL in 12.2 mL.
The prefixes are d, which means 0.1, and m, which means 0.001. Insert the values of the prefixes into the conversion.
_____ dL = 12.2 mL
_____ (0.1) L = 12.2 (0.001) L
_____ (0.1) L = 0.0122 L
To find the value of the blank, divide the right-hand number by the left-hand number.
0.0122 L ÷ 0.1 L = 0.122
This means that 12.2 mL = 0.122 dL.
