In the year 2002, the world population was estimated at 6 billion people. based on research from the world bank, about 20% lived on less than $1 per day. how many people lived on less than $1 per day?

In the given question all the information's are provided based on which the answer to the question can be easily deduced. It is already given that the population of the world in the year 2002 was estimated to about 6 billion. Among them 20% of the people lived on an an income of less that $1 per day.Firstly let us convert 6 billion from words to numbers.
6 billion = 6000000000
Now
Number of people earning less that $1 per day = (20/100) * 6000000000
                                                                           = 6000000000/5
                                                                           = 1200000000
So the number of people earning less than $1 per day is 1200000000