Suppose 8 out of every 20 students are absent from school less than five days a year.
The ratio then is 8 : 20
Predict how many students would be absent from school less than five days a year out of 40,000 students.
So the ratio now is: 8 : 20 = x : 40 000
=> 40 000 * 8 = 320 000 / 20 = 16 000
=> 8 : 20 = 16 000 : 40 000