One quantity A as a fraction of another quantity B is written as A/B and reduced to it's simplest form.
Note that the quantities must have the same units of measure. Choose th unit you find easier to work with. For example, 80 cm as a fraction of 200 cm is 80/200 = 2/5.
Note: To express 40 cm as a fraction of 2 m, first change either 40 cm to 0.4 m, or 2 m to 200 cm.
Using the latter, 40 cm as a fraction of 200 cm is 40/200 = 1/5
Note that the number which follows 'of' is the denominator.

EXAMPLE
What fraction of 600 g is 500 g.

Solution
In this example, the quantities have the same units o measure
The required answer = 500/600
                                     = 5/6


ASSIGNMENT
1. What fraction of 1 minute is 45 seconds?

2. A rod is 65 m long. 25 m is cut off. What is the remaining length?