Use the multiplier and the year 1980 as year 0 to write an equation.
226(1.02)10 = 275.5 million
See part (a).
How great is the error? Is the population growth faster or slower than expected?
How many million is one billion? Substitute this into the equation you wrote in part (a).
1000 = 226(1.02)x
4.42 = (1.02)x
You will need to guess and check to figure out x.